UC-NRLF 


B    3    112 


Wireless  Telegraphy 


and 


High  Frequency  Electricity 


E  LAV.  TWINING 


WITH  A  CHAPTER  ON 


Wireless  Telephony 

BY 

WILLIAM  DUBIUER 


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Wireless  Telegraphy 


AND 


High  Frequency 
Electricity 


MANUAL  CONTAINING  DETAILED 
INFORMATION  FOR  THE  CON- 
STRUCTION OF  TRANSFORMERS 
WIRELESS  TELEGRAPH  AND  HIGH 
FREQUENCY  APPARATUS,  WITH 
CHAPTERS  ON  THEIR  THEORY 
AND  OPERATION 


BY 


H.    LaV.   TWINING,  A.B. 

i) 

Head   of   Physics   and   Electrical   Engineering  in  the   Los  Angeles 

Polytechnic  High  School,   and  associate  member  of  the 

American  Institute  of  Electrical  Engineers 


PUBLISHED    BY    THE    AUTHOR 

1308  Calumet  Avenue,  Los  Angeles,  California 


Copyright  July  1,  1909 

by 
H.  LaV.  TWINING 


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Engineering 
Library 


PREFACE 

Many  books  have  been  written  on  induction  coils  in  which  detailed 
instruction  has  been  given  for  their  construction  and  operation. 

With  the  advent  of  wireless  telegraphy,  the  X-ray  and  high  fre- 
"quency  electricity  for  curative  purposes,  the  induction  coil  became  a 
commercial  machine. 

The  induction  coil  is  a  very  inefficient  transformer  of  energy,  but 
in  spite  of  this  it  has  proved  very  useful  to  the  medical  profession  and 
to  the  scientific  world. 

In  the  case  of  wireless  telegraphy,  however,  its  limit  was  soon 
reached.  As  long  as  wireless  communication  was  confined  to  com- 
paratively short  distances,  the  coil  answered  the  purpose  very  well. 
Long  distance  work,  however,  required  more  energy,  and  the  trans- 
former, already  developed  commercially,  was  tried  with  great  success. 

The  induction  coil  is  a  very  troublesome  instrument  on  account 
of  the  necessity  for  a  vibrator  or  a  make  and  break  device.  Its  small 
efficiency  also  renders  it  a  very  expensive  instrument,  which  places  it 
beyond  the  reach  of  many  amateurs. 

On  the  other  hand,  transformers  are  very  efficient,  and  they  can  be 
made  at  small  expense.  They  are  easy  and  convenient  to  use. 

But  few  books  have  been  written,  furnishing  the  detailed  informa- 
tion for  their  construction  and  operation.  Those  that  have  been 
written  are  large  and  expensive,  and  their  contents  are  put  in  such 
form  as  to  be  of  little  use  to  the  uninitiated. 

This  book  aims  to  furnish  the  information  in  a  clear  and  concise 
form,  so  that  anyone  can,  by  its  use,  design  and  manufacture  high 
potential  transformers  for  wireless  or  high  frequency  work. 

The  first  chapters  deal  solely  with  the  construction  of  the  trans- 
former and  other  wireless  apparatus.  This  is  followed  by  detailed  in- 
struction for  its  installation  and  operation. 

In  order  to  add  to  the  interest  and  usefulness  of  the  work,  chapters 
on  the  design  and  manufacture  of  Tesla  coils  and  Oudin  resonators 
follow. 

No  person  who  takes  up  this  fascinating  study  should  neglect  the 
theory  of  it,  if  lie  expects  to  derive  the  greatest  benefit  and  pleasure 
from  its  pursuit.  Chapters  are  added,  dealing  in  as  simple  a  way  as 
possible,  with  this  part  of  the  subject. 

Finally  fourteen  transformer  designs  are  worked  out  and  the  data 
is  collected  in  a  table,  making  it  very  convenient  for  those  who  do 
not  care  to  design  the  transformers,  themselves. 

The  detailed  method  of  design  is  given,  however,  foi;  those  who 
may  desire  to  design  larger  machines. 


250595 


A  chapter  on  station  calculation  is  added  for  those  who  may  have 
mathematical  tastes.  In  this  chapter  the  method  of  practically  cal- 
culating capacities  and  inductances  is  given,  whereby  the  wave  length 
and  frequency  of  the  station  can  be  calculated.  By  this  method  in- 
struments can  also  be  calibrated. 

The  subject  is  not  touched  upon  historically,  and  the  presentation 
of  a  great  variety  of  systems  and  their  names  is  avoided.  Only  the 
fundamental  principles  are  considered. 

Selective  tuning  has  not  been  attempted,  since  it  is  complicated, 
and  as  yet  little  understood,  but  it  is  the  problem  in  wireless  teleg- 
raphy and  telephony  today.  Without  it  they  have  reached  their  limit 
and  commercial  success  is  impossible  unless  selective  tuning  is  prac- 
ticable. 

I  desire  to  acknowledge  my  indebtedness  to  the  boys  of  Los 
Angeles,  who  have  worked  with  me  in  this  fascinating  field.  Many 
useful  things  have  been  developed  at  their  suggestion. 

The  following  boys  deserve  special  mention:  Roy  Zoll,  A.  E. 
Abrams  and  Parke  Hyde.  Roy  Zoll  is  one  of  the  pioneers  in  this 
field  in  Los  Angeles,  and  he  has  done  some  excellent  long  distance 
work.  Parke  Hdye  has  been  especially  active  in  the  construction  and 
operation  of  high  frequency  apparatus. 

Dean  Farran,  Walter  Cooper  and  George  Roalfe  put  up  the  aerial 
on  the  Polytechnic  High  School,  and  Dean  Farran  has  done  some 
excellent  long  distance  work  with  the  station  established  there.  The 
mechanical  drawings  are  the  product  of  -the  boys  of  the  Polytechnic 
High  School,  the  most  of  them  being  made  by  Sidney  Twining,  who 
also  constructed  some  of  the  apparatus. 

I  wish  also  to  express  my  appreciation  for  the  help  and  suggestions 
of  Mr.  J.  T.  LaDu,  and  Mr.  E.  J.  Ovington,  in  the  field  of  high  fre- 
quency electricity.  Mr.  Ovington  suggested  the  dimensions  of  the 
Tesla  coils  and  Oudin  resonators  that  have  proved  so  successful. 

The  following  works  have  been  freely  consulted  in  the  preparation 
of  this  bocrk:  The  Principles  of  Electric  Wave  Telegraphy,  by  J.  A. 
Flemming;  An  Elementary  Manual  of  Radiotelegraphy  and  Radio- 
telephony,  by  J.  A.  Flemming;  Wireless  Telegraphy,  by  J.  Erskine 
Murray;  and  A  Manual  of  Wireless  Telegraphy  for  the  use  of  Naval 
Electricians,  by  Lieutenant  Commander  S.  S.  Robinson,  of  the  U.S. 
Navy.  While  no  claims  are  put  forward  for  originality  in  any  of  the 
work  presented  in  this  book,  yet  everything  here  is  the  result  of  my 
own  experience,  or  the  experience  of  some  of  the  boys  with  whom  I 
have  come  in  contact.  I  shall  be  pleased  to  have  my  attention  called 
to  any  errors  that  have  crept  into  the  text,  and  I  would  consider 
it  a  favor  to  hear  from  those  who  construct  transformers  from  the 
designs  in  this  book. 

H.  LaV.  TWINING. 

Los  Angeles,  Cal.,  July  1,  1909. 


WIRELESS  TELEGRAPHY 

and  High  Frequency  Electricity 
CHAPTER  I. 

THE  TRANSFORMER 

1.  Directions. — All  of  the  data  necessary  for  the  building 
of  any  transformer,  from  a  100  watt  to  a  5  kilowatt,  is  to  be 
found  in  tables  1  and  2  in  the  back  part  of  this  book.    The  few 
pages  preceding  the  table  give  the  method  of  transformer  cal- 
culation. 

These  calculations  are  based  on  the  design  of  commercial 
power  transformers,  and  they  are  then  modified  to  fit  the  needs 
of  wireless  telegraphy.  It  is  not  necessary  for  the  reader  to 
do  the  calculating,  as  the  data  for  fourteen  transformers  are 
given'in  the  table,  but  the  method  is  given  for  the  sake  of  those 
whfo  might  wish  to  make  use  of  it. 

In  this  chapter  the  construction  of  a  transformer,  from 
the  data  given  in  the  table,  is  described,  and  for  this  purpose 
the  200  watt  transformer  is  selected. 

The  core  of  the  induction  coil  is  made  of  a  straight  bundle 
of  iron  wires,  but  the  core  of  the  transformer  is  made  of  lam- 
inations of  iron  arranged  in  the  form  of  a  rectangle,  thus  form- 
ing a  closed  magnetic  circuit. 

2.  The   Iron   Core. — For   reasons   to   be   described   later 
this  iron  core  should  be  made  of  the  best  soft  iron  to  be  had. 
This  is  called  transformer  iron.     It  is  difficult  to  obtain  any 
iron  of  this  kind,  but  the   Palmer  Electric  Company  of  Los 
Angeles  have  obtained  a  large  supply  of  this  iron  which  they 
will  sell  to  individuals  in  small  lots.     Transformer  iron  should 
be  used  by  all  means,  but  if  it  cannot  be  obtained,  the  next  best 
thing  is  ordinary  sheet  iron,  which  can  be  obtained  at  the  tin- 
smiths.    It  should  be  as  thin  as  it  is  possible  to  get  it,  but  a 
thirtieth  of  an  inch  thick  will  do.     For  the  200  watt  trans- 
former it  should  be  cut  into  strips  an  inch  wide.     Consulting 
the  table,   we  find  that  the  iron  core  should  be   10*/2    inches 
long  and  6^2  inches  wide,  outside  measure. 

Since  the  iron  is  to  be  an  inch  wide,  half  of  the  strips 
should  be  9V2  inches  long  for  the  sides  of  the  rectangle,  C  and 


8  WIRELESS  TELEGRAPHY  AND 

D,   Fig.    i,   and   the   other   half    should    be    5l/2    inches    long, 
A  and  B,  Fig.  I.    Enough  of  these  strips  should  be  obtained  to 


Fig.  1.     First  layer  of  iron  core  showing  staggering. 


Fig.  2.     Second  layer  of  iron  core  showing  staggering. 


make  the  core  when  assembled  and  tightly  pinched  together, 
about  one  inch  thick.  The  iron  should  be  assembled  according 
to  the  diagram  given  in  Fig.  i. 

The  strips  are  laid  down  in  the  form  of  a  rectangle.  The 
end  i  of  the  short  strip  B  is  placed  against  the  side  of  the 
end  2  of  the  long  strip  D.  The  end  j  of  the  long  strip  C  is 
placed  against  the  side  of  the  end  4  of  the  short  strip  B.  The 
end  5  of  the  short  strip  A  is  placed  against  the  side  of  the 
end  6  of  the  long  strip  C,  and  the  end  8  of  the  long  strip  D 
is  placed  against  the  side  of  the  end  7  of  the  short  strip  ./. 
The  second  layer  is  laid  on  top  of  this,  but  the  pieces  are  ar- 
ranged as  in  Fig.  2,  so  that  the  joints  are  staggered.  The 


HIGH  FREQUENCY  ELECTRICITY  9 

third  layer  is  laid  down  as  in  Fig.  I,  the  fourth  layer  as  in  Fig. 
2,  and  so  on  alternately.  By  following  this  plan  the  joints 
do  not  come  together  in  adjoining  layers.  The  pile  should  be 
built  up  in  this  way  until  it  is  an  inch  thick. 

The  end  A,  however,  should  be  left  out  and  staggered  into 
place  after  the  coils  are  placed  on  the  core.  Fig.  3  shows  a 
photograph  of  the  iron  core  thus  assembled  and  taped. 

3.  Insulation. — When  the  laminations  are  assembled  they 
should  be  bound  together  with  friction  tape  leaving  out  the 
end  piece  A.     The  iron  when  thus  bound  will  hold  together 
at  the  ends,  /,  2,  and  j,  4,  Fig.  2.    The  tape  should  be  wound 
around  the  iron  tightly  and  be  overlapped  as  shown  in  the 
figure.      Long   strips   of   empire   cloth,   8.  mils   thick   and   8^2 
inches  wide  should  be  tightly  wound  around  the  legs  C  and  D 
of  the  core  until  at  least  10  layers  are  placed  in  position.     They 
should  then   be   taped  as  shown   in  Fig.  5   in   order  to  hold 
them  in  place. 

It  is  necessary  to  thoroughly  insulate  the  iron  from  the 
coils.  No  half  way  measures  will  do.  When  the  transformer 
is  in  operation,  high  voltage  surges,  from  the  oscillation  cir- 
cuits, strike  back  into  the  transformer,  and,  unless  the  latter 
be  highly  insulated,  it  will  break  down. 

The  primary  should  be  just  as  thoroughly  insulated  as  the 
secondary.  This  layer  of  empire  cloth  should  be  about  %  of 
an  inch  thick. 

4.  The  Primary. — By  referring  to  tables   1   and  2,  it  is 
seen  that  666  turns  of  number  15  double  cotton  covered  magnet 
wire  is  necessary  for  the  primary.    In  an  ordinary  power  trans- 
former, these  turns  would  be  made  of  a  smaller  wire,  with 
1,200  turns  instead  of  666  turns;  but  in  this  case  less  turns 
are  used  and  more  amperes  are  allowed  to  flow,  thus  accom- 
plishing the   same   result.     This  works   the   iron   at  a  higher 
density.     Larger  wire  has  to  be  used  in  order  to  carry  the 
increased  amperage  without  undue  heating. 

In  order  to  build  the  primary,  it  is  necessary  to  have  a 
form  upon  which  to  make  the  windings.  Fig'.  4  shows  the 
details  of  such  a  form*.  Prepare  a  rectangular  block  15  inches 


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HIGH  FREQUENCY  ELECTRICITY  11 

long  and  about  \y2  inches  square,  depending  upon  the  dimen- 
sions of  the  insulated  leg  of  the  iron  as  found  in  Fig.  5. 
,Turn  down  a  shoulder  on  each  end,  making  the  rectangular 
portion  A  7y2  inches  long. 

Since  the  outside  dimensions  of  the  core  are  \Ol/2  inches 
and  the  iron  is  1  inch  wide,  it  is  necessary  to  subtract  two 
inches  to  get  the  inside  dimensions  of  the  core. 

The  primary,  when  wound  and  placed  in  position,  should 
have  its  ends  at  least  y2  inch  away  from  the  iron  ends  of  the 
core.  This  requires  another  inch  of  space  so  that  1  inch 
more  must  be  subtracted.  This  makes  the  primary  winding 
7y2  inches  instead  of  9l/2  inches,  as  shown  in  the  cut. 

The  rectangular  portion  A,  then,  should  be  7l/2  inches 
long.  The  end  shoulders  designated  as  H,  E  and  F,  in  Fig  4, 
can  be  either  square  or  round.  Prepare  two  circular  blocks 
B  and  D  y\  inch  thick  and  ^y2  inches  in  diameter.  Cut  out 
a  hole  H  to  fit  the  shoulders  E  and  F.  With  a  saw  split  the 
rectangular  block  A  along  the  line  EAF,  cutting  the  block  into 
two  wedge-shaped  pieces.  Slip  on  the  two  circular  end  pieces 
and  fasten  firmly  in  position. 

Over  the  rectangular  part  A  place  a  couple  of  thicknesses 
of  paper  so  that  the  coil  can.  slip  off  the  block  easily  when 
finished.  At  L  in  each  block  bore  a  series  of  holes  large  enough 
to  admit  the  number  15  wire. 

Chuck  the  form  in  the  lathe.  If  no  lathe  is  at  hand,  the 
shoulders  E  and  F  should  be  made  rounch  Take  two  pieces 
of  two-by-four  and  bore  holes  an  inch  from  the  end  of  each. 
Place  the  shoulders  E  and  F  in  these  holes,  and  fix  the 
two-by-fours  firmly  in  position,  either  upright  or  horizontally. 
They  can  be  nailed  to  a  bench  if  desired.  This  will  do  just  as 
well  as  the  lathe  for  winding. 

Put  one  end  of  the  wire  through  the  hole  at  L  from 
the  inside  outward,  allowing  about  six  inches  of  free  end  to 
protrude.  A  rod  of  iron  or  wood  should  be  run  through  the 
center  of  the  spool  containing  the  wire  to  be  wound  on  the 
form,  and  this  should  be  supported  so  that  the  spool  will  un- 
wind freely,  as  the  winding  progresses.  With  the  wire  in  the 
right  hand,  and  the  left  hand  on  D,  proceed  to  turn  the  form 


12  WIRELESS  TELEGRAPHY  AND 

away  from  you,  winding  the  wire  on  tightly  and  evenly  from 
the  end  B  to  the  end  D. 

Have  some  hot  paraffine  at  hand  and  paint  the  winding 
with  it.  The  paraffine  will  hold  the  windings  firmly  in  place. 
Keep  on  with  the  winding,  putting  the  second  layer  on  top  of 
the  first,  back  to  the  point  of  beginning. 

Upon  reaching  B  with  the  second  layer,  cut  the  wire  and 
bring  out  a  terminal  I,  six  inches  long.  There  are  now  222 
turns  on  the  coil.  For  the  third  layer  put  the  end  of  the  wire 
through  the  hole  /  and  solder  it  to  terminal  7.  This  forms 
the  first  tap. 

Wind  on  this  layer  from  left  to  right  and  upon  reaching 
D  cut  the  wire  and  bring  out  the  terminal  2.  Through  the 
same  hole  put  the  wire  for  the  next  layer,  soldering  it  to  2. 
Proceed  in  this  manner. until  six  layers  have  been  put  on, 
bringing  out  taps  at  5  and  4,  ending  finally  with  5.  These 
taps  should  be  labeled  as  designated  in  the  figure  so  that  no 
mistakes  can  occur. 

They  should  be  carried  to  the  adjustable  rheostat  on  the 
cover  of  the  transformer,  Figs.  12  and  7j.  We  thus  have  an 
adjustable  rheostat  on  the  primary  of  the  transformer  itself, 
consisting  of  222  turns  on  the  first  tap,  333  turns  on  the  second 
tap,  444  turns  on  the  third  tap,  555  turns  on  the  fourth  tap,  and 
666  turns  on  the  terminal  5. 

With  the  666  turns  cut  in,  this  transformer  will  develop 
about  5,890  volts  on  the  secondary  and  3.6  amperes  will  flow. 
As  the  turns  are  cut  out  more  amperes  will  flow  and  higher 
voltages  will  be  developed  on  the  secondary.  With  the  222 
turns  cut  in,  17,621  volts  will  be  developed  on  the  secondary. 

If  desired,  222  turns  only  need  be  put  on  the  primary 
and  this  will  require  only  11,879  turns  on  the  secondary  in- 
stead of  35,564  turns  in  order  to  develop  5,890  volts  on  the 
secondary. 

All  of  the  transformers  given  in  the  table  1  up  to  the  two 
kilowatt  can  be  modified  in  this  way,  making  them  much 
cheaper.  In  this  case  an  impedence  or  a  water  resistance  must 
be  put  in  series  with  the  primary  to  choke  back  the  current, 
as  will  be  explained  later.  I  much  prefer  the  second  method, 


HIGH  FREQUENCY  ELECTRICITY 


13 


as  the  amperages  and  voltages  can  be  much  better  controlled 
by  the  impedence  or  water  rheostat. 

Take  the  completed  coil  off  the  lathe.  Remove  the  end 
blocks,  pulling  the  wires  out  through  the  holes,  which  should 
have  been  made  large  enough  so  that  this  can  be  easily  done. 
The  coil  should  now  be  taped  lengthwise  with  either  cotton 
or  friction  tape.  When  completed  it  is  to  be  thrust  over  the 
leg  D  of  the  iron  core  as  shown  in  Fig.  u.  The  ends  of  the 
coil  should  be  ^  inch  away  from  the  iron.  It  will  require 
about  Zl/2  pounds  of  number  fifteen  wire  to  put  on  the  666 
turns  and  about  one-third  as  much  to  put  on  the  222  turns. 


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Fig.  5.     Form  for  winding  secondary. 


5.  The  Secondary. — If  666  turns  are  put  on  the  primary, 
it  will  require  about  6T/2  pounds  of  number  thirty-four  double 
cotton  covered  magnet  wire.  If  200  turns  are  used  on  the 
primary,  it  will  be  necessary  to  use  only  3  pounds  of  the 
number  34  wire,  D.  C.  C.,  in  order  to  develop  8,000  volts. 
This  would  require  14,513  turns  on  the  secondary. 

3,000  to  5,000  volts  in  a  transformer  is  all  that  is  necessary 
for  a  transformer  for  wireless  or  high  frequency  demonstra- 
tions, especially  for  all  transformers  up  to  the  kilowatt  size, 
but  the  higher  voltages  are  better  for  large  pieces  of  apparatus 
or  very  large  aerials. 

If  the  smaller  number  of  turns  are  put  on,  the  core  does 


14  WIRELESS  TELEGRAPHY  AND 

not  need  to  be  as  long  nor  as  wide  as  in  the  other  case,  and 
it  should  be  modified  accordingly. 

6.  The  Form. — A  form  is  necessary  upon  which  to  wind 
the  secondary.  The  secondary  coils  should  be  wound  in  flat 
pie  coils.  The  form  for  this  is  shown  in  detail  in  Fig.  5. 

Cut  two  circular  blocks  A  and  B  1  inch  thick  and  8  inches 
in  diameter.  The  coils  are  to  be  made  V^  of  an  inch  thick. 
They  should  not  be  made  any  thicker  than  this.  If  they  are 
made  too  thick,  they  will  break  down  between  turns  and  all 
the  work  will  have  to  be  done  again. 

Prepare  a  little  block  C  one-quarter  of  an  inch  thick  and 
about  \l/2  inches  square.  This  square  ^should  be  large  enough 
so  that  the  coil  when  wound  will  slip  easily  on  to  the  insulated 
leg  of  the  transformer. 

Obtain  a  bolt  N  2l/2  to  3  inches  long.  ,  Bore  holes  through 
the  centers  of  the  blocks  A,  B  and  -C  large  enough  to  admit 
the  bolt.  Screw  the  circular  block  A  to  the  face  plate  F  and 
nail  the  block  C  to  the  block  A. 

Cut  out  two  circular  pieces  of  paper  and  make  square 
holes  in  their  centers  the  size  of  the  block  C.  Paste  them  on 
to  the  inner  surfaces  of  A  and  B  with  hot  paraffine. 

The  circumference  of  the  block  C  should  not  be  per- 
pendicular to. A,  but  it  should  slope  slightly  from  A  to  B,  so 
that  the  coil  when  wound  can  slip  off  the  form  easily.  On  the 
circumference  of  C  paraffine  a  piece  of  paper,  so  the  coil  can- 
not stick  to  the  wood. 

Bore  a  hole  through  the  plate  B  at  D,  through  which  to 
put  the  end  of  the  wire.  Bolt  the  plates  thus  prepared  to  the 
face  plate  F,  as  shown  in  the  figure. 

By  means  of  the  face  plate,  scre\v  the  form  to  the  lathe. 
If  no  lathe  is  at  hand,  then  an  arrangement  similar  to  that 
for  winding  the  primary  should  be  made.  The  more  slowly 
the  coils  are  wound,  the  more  turns  it  is  possible  to  get  in  a 
given  space. 

Melt  two  or  three  pounds  of  paraffine  in  a  galvanized  iron 
pail  and  place  the  spool  of  number  thirty-four  wire  into  the 
hot  paraffine,  and  let  it  stay  there  until  it  is  thoroughly  heated. 


HIGH  FREQUENCY  ELECTRICITY  15 

Take  it  out  and  run  a  rod  through  a  hole  bored  through  the 
center  of  the  spool. 

Take  two  blocks  a  foot  in  length  and  bore  holes  near  their 
ends  large  enough  to  receive  the  ends  of  the  rods.  Fix  the 
blocks  in  an  upright  position  and  run  the  ends  of  the  rod 
through  the  holes,  so  that  the  spool  can  unwind  freely  as  the 
wire  is  wound  onto  the  form. 

On  the  form  thus  prepared,  wind  about  an  eighth  of  an 
inch  of  paraffined  string.  Put  the  free  end  of  the  wire  through 
the  little  hole  D,  Fig.  5,  from  the  inside  outward,  leaving  the 
free  end  about  a  foot  long.  Drive  a  tack  into  the  outside 
of  the  form  and  secure  the  wire  to  it. 

7.  The  Winding. — Begin  to  wind,  turning  the  form  away 
from  you.  If  you  have  a  lathe,  the  winding  can  be  done  very 
rapidly,  but  it  will  be  done  at  the  expense,  of  less  turns  in  a 
given  space.  If  the  winding  be  done  slowly  by  hand,  the 
turns  can  be  laid  on  more  evenly,  and  as  they  will  not  cross 
one  another  so  much  as  in  the  rapid  winding,  many  more 
turns  can  be  put  on.  The  number  of  turns  given  in  the  table 
is  for  the  fairly  slow  winding. 

Proceed  to  wind  until  the  form  is  filled  to  a  depth  of  two 
inches.  If  the  wire  on  the  spool  begins  to  get  cool  before  the 
winding  is  completed;  take  the  spool  off  the  rod  without 
breaking  the  wire,  and  put  it  in  the  hot  paraffine  for  a  short 
time. 

If  the  spool  is  kept  in  the  paraffine  during  the  winding, 
too  much  paraffine  will  go  on  to  the  form  with  the  wire,  and 
this  will  reduce  the  number  of  turns  that  can  be  put  on  the 
form.  The  paraffine  makes  the  wire  stick  together  so  that  it 
can  be  easily  removed  from  the  form  without  falling  apart. 

During  the  winding  of  the  coil,  it  should  be  tested  from 
time  to  time  to  see  whether  it  is  open.  The  wire  may  be 
broken  and  hold  together  firmly  because  of  the  cotton  insula- 
tion. If  a  ringing  testing  set  is  at  hand,  this  can  be  done 
without  cutting  the  wire  or  disturbing  the  insulation.  Attach 
the  free  end  of  the  coil  to  one  binding  post  of  the  testing  set. 
AUach  another  wire  to  the  other  binding  post,  and,  to  the  free 


WIRELESS  TELEGRAPHY  AND 


HIGH  FREQUENCY  ELECTRICITY  17 

end  of  this  wire  attach  a  sharp  metallic  point.  This  point  can 
be  thrust  through  the  insulation  at  any  place  on  the  wire  and 
the  bell  can  be  rung  in  the  usual  way.  If  you  have  no  testing 
set,  make  one  in  the  following  manner: 'Make  a  form  of  wood 
two  inches  wide,  three  inches  long  and  an  inch  thick.  Paraffine 
some  paper  onto  the  wood.  Then  put  two  or  three  layers  of 
unparaffined  paper  over  this.  Wind  on  this  form  from  five 
hundred  to  a  thousand  turns  of  the  thirty-four  wire,  or,  better 
still,  the  same  number  of  turns  of  number  thirty-six  wire. 
When  the  winding  is  completed,  drive  out  the  form  and  tape 
the  coil.  Obtain  a  pocket  compass  and  put  inside  of  the  coil. 
Bring  the  terminals  of  the  coil  to  binding  posts,  and  you  have 
a  cheap  testing  set.  Use  one  or  two  dry  cells  on  this  galva- 
nometer. A  telephone  and  battery  can  be  used  instead  of  the 
above.  This  is  the  best  method. 

Having  completed  the  winding  of  the  coil,  remove  the 
form  from  the  head,  take  out  the  bolt,  and,  with  the  thin 
blade  of  a  table  knife,  loosen  the  outside  circular  block  of  the 
form,  inserting  the  blade  of  the  knife  under  the  paper  next 
to  the  wood  and  not.  next  to  the  wires.  The  paper  separates 
easily  from  the  wood.  In  the  same  way  separate  the  coil  from 
the  other  block  of  the  form.  Test  the  coil  to  see  that  it  is 
not  open. 

8.  Taping  the  Coils. — Obtain  empire  cloth  about  eight 
mils  thick  and  cut  it  into  strips  about  three-fourths  of  an  inch 
wide.  Do  not  cut  the  cloth  parallel  to  the  edge  of  the  sheet, 
but  cut  it  in  strips  from  corner  to  corner.  It  will  be  much 
stronger  if  cut  in  this  way. 

To  put  on  the  tape,  take  the  coil  in  the  left  hand,  see 
Fig.  6,  letting  the  outer  terminal  of  the  coil  run  to  the  left  and 
the  inner  terminal  toward  the  right.  Take  the  tape  in  the  right 
hand  and  place  one  end  about  the  middle  of  the  upper  side  of 
the  coil,  as  shown  in  the  cut.  Carry  the  tape  away  from  you 
around  the  coil,  allowing  it  to  lap  over  about  half  of  its  width. 
When  the  end  of  the  strip  is  reached,  place  the  end  of  another 
strip  on  top  of  the  end  of  the  strip  just  put  on  and"  proceed 
with  the  taping. 


18 


WIRELESS  TELEGRAPHY  AND 


As  you  reach  the  point  of  beginning,  allow  the  inner 
terminal  of  the  coil  to  run  on  around  in  the  way  in  which  it 
is  wound,  so  that  it  will  come  out  of  the  taped  coil  in  the  same 
direction  in  which  it  is  wound,  as  shown  in  Fig.  8. 

The  tape  should  now  be  wound  close  up  to  the  outer 
terminal,  leaving  it  free.  Do  not  wind  it  in  as  was  done 
with  the  inner  terminal.  Allow  this  terminal  to  come  out 
of  the  tape  in  the  same  direction  in  which  it  is  running  around 
the  coil,  as  shown  in  Fig.  8.  The  tape  can  now  be  carried 
beyond  the  outer  terminal  a  short  distance  until  the  inner 
terminal  is  well  taped  in  as  shown  in  the  cut.  The  free  end 
of  the  tape  should  now  be  tucked  under  the  last  turn  of  the 
tape  and  drawn  tightly.  If  the  coil  is  taped  in  this  way,  the 
direction  in  which  the  wife  is  wound  on  the  coils  is  easily  seen 
without  taking  off  any  of  the  tape.  This  will  save  trouble. 


Fig.  8.    Secondary  coil,  showing  taping  complete. 


HIGH  FREQUENCY  ELECTRICITY  19 

In  bringing  out  the  terminals,  care  should  be  taken  not  to 
let  the  wire  kink  up  as  shown  in  Fig.  /,  so  as  to  cross  any 
of  the  turns  of  the  coil,  as  there  is  danger  of  the  coil  breaking 
down  across  the  turns.  In  this  manner  make  twenty-six  coils. 

9.  Assembling  the  Coils. — Before  assembling  the  coils  on 
the  core,  they  should  be  grouped  together  in  pairs,  the  insides 
of  the  coils  being  joined  together,  as  in  Fig.  p.  If  the  current 
be  supposed  to  enter  the  coil  A  at  D,  the  inside  of  A  should 
be  joined  to  the  inside  of  B,  so  that  the  current  runs  around 
the  core  in  the  same  direction  as  it  is  running  in  A.  In  order 
to  accomplish  this,  put  the  coil  A  on  top  of  the  coil  B  so  that 
the  two  free  ends,  D  and  C,  are  running  in  opposite  directions. 


D 


A  B 

Fig.  9.     Method  of  joining  coils  in  pairs. 

If  this  latter  point  is  attended  to,  there  will  be  no  danger 
of  getting  them  together  wrong.  All  connections  should  be 
soldered.  Before  assembling  these  coils  in  pairs,  cut  circular 
discs  of  empire  cloth,  an  inch  larger  in  circumference  than  the 
taped  coils.  Cut  out  their  centers  so  that  they  will  fit  over  the 
core  of  the  transformer.  Put  two  of  these  between  the  two 
coils  of  each  pair. 

After  they  are  joined  in  pairs,  assemble  the  pairs  on  the 
core,  so  that  the  end  C  of  the  second  coil  of  the  first  pair  joins 
to  the  beginning  G  of  the  first  coil  of  the  second  pair,  con- 
tinuing on  around  the  core  in  the  same  direction.  This  is 
easily  accomplished,  if  the  end  of  one  pair  and  the  beginning  of 


20 


WIRELESS  TELEGRAPHY  AND 


the   other  pair  are   coming  out   in   opposite   directions,   as   in 
Fig.  10. 

If  A  and  B  are  the  first  pair  and  E  and  F  are  the  second 
pair,  then  the  end  C  of  the  first  pair  should  join  to  the  begin- 
ning G  of  the  first  coil  of  the  second  pair.  The  inside  of  E 


B  E 

Fig.    10.      Method   of  joining   pairs. 


is  connected  to  the  inside  of  F  as  in  the  first  pair,  coil  E 
being  placed  on  top  of  the  coil  F.  Thus  D  and  H,  the  be- 
ginning and  end  of  the  four  coils,  come  out  in  opposite  direc- 
tion, and  the  wire  is  running  around  the  core  in  the  same 
direction. 

•  Each  pair  should  be  assembled  in  the  same  manner  rela- 
tive to  the  pair  before  it.  Four  discs  of  empire  cloth  should 
be  put  between  each  pair  of  coils.  In  assembling  the  pairs,  it 
should  be  noticed  that  the  outside  end  of  one  pair  in  connect- 
ing to  the  outside  end  of  the  adjoining  pair  should  not  turn 
back.  If  it  does,  it  is  wrong;  it  should  continue  on  around 
and  not  turn  back  on  itself. 

When  assembled,  the  coils  should  not  be  pinched  tightly 
together.  They  should  be  loose  so  that  the  oil  or  wax  can  get 
clown  between  them  easily.  In  order  to  keep  them  apart  they 
can  be  wound  with  string,  as  shown  in  Fig.  if.  If  the  trans- 
former is  to  be  in  continual  use,  these  coils  should  be  assem- 
bled so  that  the  oil  in  which  they  are  to  be  immersed  can  cir- 
culate all  around  them. 

This  can  be  easily  arranged  in  the  following  manner: 
Cut  a  circular  disc  of  stiff  fullerboard  about  an  inch  greater 
in  diameter  than  the  taped  coils.  Cut  a  circular  hole  in  the 
center  of  it,  so  that  it  will  fit  snuu'lv  over  the  insulated  lei; 


HIGH  FREQUENCY  ELECTRICITY  21 

of  the  transformer.  Take  the  paraffined  string  off  the  inside 
of  the  coils  before  taping  them. 

Wind  coarse  thread  or  string  around  each  taped  coil  in 
the  same  way  as  the  tape  is  wound,  but  the  string  should  not 
be  wound  tightly  together.  Let  each  turn  of  the  string,  be 
from  a  quarter  to  a  half  of  an  inch  apart.  See  Fig.  ij.  Place 
the  fullerboard  between  the  coils  thus  prepared,  and  wind 
string  around  the  coils  and  fullerboard,  binding  the  coils  firmly 
to  the  board. 

The  coils  are  thus  held  one-eight  of  an  inch  away  from 
the  core  of  the  transformer.  The  thread  keeps  the  coils  from 
fitting  tightly  to  the  fullerboard.  Assemble  the  pairs  thus 
prepared  on  the  core,  putting  four  thicknesses  of  empire  cloth 
between  the  pairs,  or  put  one  thickness  of  fullerboard  between 
them  and  two  thicknesses  of  empire  cloth. 


Fig.   11.     Transformer  core  with   primary  and  one   pair   of   secondary 

coils   in   place. 


22  WIRELESS  TELEGRAPHY  AND 

When  arranged  in  this  manner,  the  oil  can  circulate  all 
around  the  coils  without  obstruction.  The  oil  not  only  insulates 
them  well,  but  it  also  cools  the  coils  by  circulating.  The  hot  oil 
rises  to  the  top  and  flows  over  to  the  side  of  the  case,  where 
it  is  cooled  and  returned  to  the  coils  again.  If  the  transformer 
is  to  be  in  constant  use,  this  is  necessary. 

Fig.  ii  is  a  photograph  of  a  kilowatt  transformer,  with 
the  primary  in  place  on  the  lower  leg.  The  upper  leg  has  one 
pair  of  the  coils,  just  described,  in  place.  These  coils  are  not 
taped.  String  is  wound  around  them  and  they  are  then  fast- 
ened to  the  fullerboard  by  string,  as  described  above.  This 
allows  the  oil  to  come  directly  in  contact  with  the  coils.  On 
this  account  this  is  better  than  taping  them.  More  empire 
cloth  should  be  put  between  the  pairs  of  coils  than  in  the 
other  case.  Taping  the  coils  makes  them  mechanically 
stronger,  however,  and  they  are  less  liable  to  injury. 

The  first  and  last  coil  of  the  secondary  should  be  from  a 
half  inch  to  an  inch  away  from  the  end  iron  of  the  trans- 
former core.  Before  assembling  the  coils  on  the  core,  it  is 
well  to  put  two  or  three  thicknesses  of  fullerboard  and  as 
many  of  empire  cloth  next  to  the  iron,  and,  when  the  coils 
are  all  assembled,  put  on  the  same  amount  before  staggering 
in  the  end  pieces.  If  the  latter  method  of  assembling  the 
coils  is  used,  they  should  be  pushed  snugly  together,  but 
not  pinched  tightly,  and  the  ends  between  the  end  coils  and 
the  iron  can  be  filled  with  wooden  wedges  previously  boiled 
in  oil  to  expel  air  and  moisture.  These  wedges  hold  the  coils 
firmly  in  place.  The  latter  method  is  much  the  better  method 
for  assembling  the  coils,  even  if  they  are  to  be  put  up  in 
the  wax  preparation.  The  end  pieces  should  be  s-taggered  into 
place  as  soon  as  the  coils  are  assembled,  thus  completing  the 
magnetic  circuit. 

10.  Insulation. — The  wax  preparation  for  imbedding  the 
transformer  is  made  as  follows :  One  pound  of  beeswax,  one 
and  one-half  pounds  of  paraffine  and  four  pounds  of  rosin. 
Melt  in  a  galvanized  iron  dish  until  thoroughly  mixed.  Then 
heat  until  all  moisture  is  driven  off.  If  too  brittle,  use  less 


HIGH  FREQUENCY  ELECTRICITY 


23 


rosin.  If  too  soft,  use  less  paraffine.  The  beeswax  is  quite 
expensive  and  can  be  omitted.  Petrolatum  or  vaseline  can 
be  used  to  advantage,  about  one  part  in  seven  being  mixed 
with  the  other  ingredients. 


o 

6 


Fig.  12.     Transformer  connections  where  binding  posts  are  used. 

I,   alternator   supplying   the    current;    L,   lead   to   binding  post   F2; 
1,  2,  3,  4  and  5,  binding  posts;   I,  II,  III,  IV,  V,  taps;   R,  adjustable 
lead;  Q,  coils  on  core. 


24  WIRELESS  TELEGRAPHY  AND 

If  the  transformer  is  small,  it  can  be  conveniently  put 
in  a  box  of  the  proper  size  and  the  hot  wax  poured  in  around 
it  and  allowed  to  cool.  If  the  transformer  is  to  be  put  in  oil 
or  if  it  is  a  large  one,  a  galvanized  iron  box  is  necessary. 
Double  boiled  linseed  oil  or  transformer  oil  can  be  used. 
The  taps  from  the  primary  should  be  brought  out  to  binding 
posts  on  the  cover  in  the  manner  described  below. 

\ 

11.  Rheostat. — If  the  voltage  of  the  secondary  is  below 
twenty  thousand,  and  the  cover  is  a  wooden  one,  the  secondary 
taps  can  be  brought  to  binding  posts  on  the  cover.  If  it  is 
above  twenty  thousand,  bring  the  secondary  terminals  out 
through  hard  rubber  tubes. 

Fig.  12  is  a  diagram  of  the  connections.  /  is  the  alter- 
nator that  supplies  the  current  for  the  house  or  the  socket  into 
which  the  leads  L  and  R  are  plugged.  F 2  is  the  binding  post, 
which  is  connected  to  the  terminal  marked  L  of  Fig.  4.  It 
conies  from  the  coil  nearest  the  core. 

I,  2,  3,  4  and  5  are  the  binding  posts  to  which  the  taps 
i,  2,  3,  4  and  5  of  Fig.  4  are  taken.  They  are  represented  in 
this  figure  by  the  characters  /,  //,  ///,  IV  and  V.  The  lead 
R  is  adjustable  so  that  it  can  be  attached  to  the  post  /,  2,  3, 
4  or  5.  When  attached  to  i,  the  highest  voltage  is  developed, 
.as  only  two  coils  are  then  cut  in.  When  attached  to  2,  three 
coils  are  cut  in,  etc.,  until  all  the  coils  are  cut  in  at  5. 

This  diagram  represents  the  primary  connections  only. 
The  secondary  terminals  should  be  brought  out  as  far  as 
possible  from. the  primary  and  should  be  attached  to  binding 
posts.  This  arrangement  can  all  be  put  on  the  cover  of  the 
transformer.  When  two  coils'  only  are  cut  in,  they  should  be 
those  nearest  the  core.  All  connections  should  be  soldered, 
even  to  the  binding  posts  from  the  taps. 

In  Fig.  13  the  connections  are  shown  for  a  rheostat  to 
be  located  on  the  cover  of  the  transformer.  The  leads  L  and 
Lr  come  from  the  source  of  electrical  energy  and  attach  to 
the  binding  posts  F  and  FT.  The  binding  post  F  is  connected 
to  the  tap  marked  L  in  Fig.  4.  The  binding  post  /;/  is  attached 


HIGH  FREQUENCY  ELECTRICITY 

Q 


25 


Fig.  13.     Primary  transformer  connections  to  rheostat  on  cover. 

L,  Li,  leads  from  plug  to  binding  posts;  F,  Fj,  binding  posts; 
P  to  Q,  coils  of  primary;  I,  II,  III,  IV,  V,  taps  from  primary  coils 
leading  to  points  1,  2,  3,  4  and  5;  NM,  curved  brass  contact  piece; 
WM,  wiper;  X,  knob  of  rubber  for  turning  wiper;  O,  off  point; 
1,  2,  3.  4,  5,  contact  points. 

to   a   curved    brass   piece   NM,    upon    which    one    arm   of   the 
wiper  XM  slides. 

The  other  end  of  the  wiper  rests  on  the  off  point  0. 
This  point  is  not  connected  to  anything  and  when  the  arm 
of  the  wiper  rests  on  it,  the  circuit  is  open.  By  means  of 


26  WIRELESS  TELEGRAPHY  AND 

the  knob  X,  the  wiper  can  be  turned  so  as  to  rest  on  /,  2,  J, 
^  or  5  successively,  thus  cutting  in  more  and  more  turns,  until 
they  are  all  cut  in.  When  resting  on  /,  two  coils  are  cut  in ; 
on  2,  three  coils,  etc.  The  points  o,  /,  2,  j,  4  and  5  should  be 
made  of  brass  turned  out  in  the  lathe.  The  heads  should  be 
a  quarter  of  an  inch  in  diameter,  at  least,  and  an  eighth  of  an 
inch  thick.  The  part  that  goes  through  the  wood  should  be 
one-eighth  inch  in  diameter,  and  long  enough  to  go  through 
the  wood.  Thread  this  part  and  make  a  couple  of  nuts  to 
fit  it.  Machine  screws  can  be  used  for  this  purpose  if  you 
have  no  lathe.  Obtain  screws  of  the  right  size  and  file  the 
tops  down  flat.  They  should  be  put  near  enough  together  so 
that  the  arm  W  makes  contact  with  one  before  it  leaves  the 
other,  otherwise  the  point  of  the  wiper  will  fall  down  between 
two  points.  This  should  never  be  adjusted  while  the  trans- 
former is  running,  or  the  coils  will  be  short  circuited  and  this 
would  burn  out  the  transformer. 

The  wiper  W  can  be  made  of  one-sixteenth  inch  spring 
brass,  or  better  of  phosphor  bronze.  The  knob  X  should  be 
turned  out  of  rubber  or  fiber.  Bore  a  hole  an  eighth  of  an 
inch  in  diameter  through  the  phosphor  bronze  strips  MW . 
Take  a  piece  of  one-eighth  inch  brass  rod,  long  enough  to  go 
through  and  beyond  the  wood  of  the  cover  a  quarter  of  an  inch. 
It  should  also  project  a  half  an  inch  into  the  knob  X.  Insert 
it  through  the  hole  in  WM  and  solder  it  firmly  in  position. 
Thread  both  ends  of  the  brass  rod.  Bore  a  hole  in  the  knob 
and  thread  it  to  fit.  Screw  it  on  to  the  upper  side  of  WM. 

Obtain  a  brass  tube  -that  will  allow  the  one-eighth  inch 
brass  rod  to  be  thrust  through  it.  Cut  it  off  the  proper 
length  to  form  a  sleeve  for  the  rod  to  turn  in. 

Bore  a  hole  in  the  wood  a  little  smaller  than  the  sleeve 
and  drive  it  tightly  into  position.  Insert  the  rod  and  screw 
a  nut  on  from  below.  Head  it  on  so  that  it  cannot  come  off. 

Stops  should  be  placed  at  M  and  TV  to  prevent  the  arm 
XM  from  sliding  off  the  brass  piece  NM. 

12.  Impedance. — This  rheostat  as  described  here  is  an 
excellent  one  for  impedence.  The  impedance  is  built  just  the 


HIGH  FREQUENCY  ELECTRICITY  27 

same  as  a  transformer,  except  that  no  secondary  is  wound  on 
it.  In  this  case  F  and  Fi  are  connected  in  series  with  the 
primary  of  the  transformer  with  which  it  is  to  be  used. 

These  high  potential  transformers  should  be  put  up  in 
oil  or  wax  preparation.  If  they  are  below  10,000  volts 
on  the  high  side  and  are  carefully  insulated,  they  will  stand 
it  for  a  while  without  breaking  down ;  but  there  is  a  static 
discharge  developed  between  the  coils  of  the  secondary,  that 
will  sooner  or  later  cause  it  to  break  down.  The  only  safe 
way  is  to  fix  them  so  they  cannot  break  down. 

Leads  of  flexible  lamp  cord  should  be  soldered  to  the  ter- 
minals of  the  primary  and  secondary,  and  these  should  be 
soldered  to  the  rheostat  terminals  on  the  cover. 

The  leads  should  be  long  enough  so  that  the  cover  can 
be  held  at  least  at  an  angle  of  sixty  degrees  while  doing  the 
soldering.  After  all  is  finished,  a  hot  preparation  of  the  wax 
should  be  poured  into  the  box  containing  the  transformer, 
until  it  is  covered  to  the  depth  of  an  inch.  As  it  cools,  add 
more  of  the  preparation,  since  it  shrinks  on  cooling.  When 
cool  lower  the  cover  and  screw  in  position. 

13.  Voltages. — If  a  high  voltage  transformer  is  desired, 
it  is  not  necessary  to  put  666  turns  on  the  primary ;  222  turns, 
only,  will  do,  but  an  impedence  or  water  rheostat  must  be 
used  in  series  with  the  primary  to  regulate  the  flow  of  current. 

In  this  transformer  5,890  volts  are  developed  in  the 
secondary  with  666  turns  in  the  primary,  and  35,564  turns  in 
the  secondary;  555  turns  develop  7,048  volts;  444  turns  de- 
velop 8,810  volts;  333  turns  develop  11,741  volts;  and  222 
turns  develop  17,621  volts. 

This  transformer  is  designed  to  stand  20,000  volts.  I  have 
found  the  10,000  volts  to  be  better  than  20,000  for  working 
the  high  frequency  apparatus  described  in  this  book.  It 
gives  more  amperes  in  the  secondary. 

In  the  above,  double  cotton  covered  wire  is  used.  Single 
cotton  cover  will  raise  the  voltage  to  7,300  at  the  lowest,  to 
22,000  at  the  highest.  For  higher  voltages,  increase  the  length 
of  the  core  and  put  on  more  coils. 


28  WIRELESS  TELEGRAPHY  AND 

14.  A  Very  Cheap  Transformer. — A  very  cheap  trans- 
former that  will  work  well  can  be  made  by  changing  this 
design  a  little.  Make  the  iron  core  Sy2  inches  wide  by  8j/2 
inches  long,  with  a  square  inch  cross  section  as  before,  Wind 
the  secondary  coils  to  a  depth  of  1  inch  or  a  little  more.  This 
will  put  on  1,000  turns  per  coil.  Make  10  of  these  coils  in- 
stead of  17  or  18  as  in  the  former  case. 

Wind  on  the  primary  two  layers,  one  of  110  turns,  and 
bring  out  a  tap.  Put  on  the  other  layer  of  110  turns,  thus 
giving  220  turns  in  all.  The  110  turns  will  give  10,000  volts 
and  the  220  turns  will  give  5,000  volts. 

Put  a  water  rheostat  in  series  with  the  primary  and  regu- 
late the  current.  With  a  200-watt  transformer  of  this  type 
and  2l/2  amperes  flowing  in  the  primary,  one  can  send  30 
miles  overland  from  a  200-foot  horizontal  aerial  40  feet  above 
ground,  or  30  miles  with  a  70-foot  vertical  aerial. 

A  transformer  of  this  kind  will  not  cost  more  than  seven 
dollars  and  a  half  for  the  materials.  All  of  the  designs  given 
in  the  table  can  be  modified  in  this  way.  In  every  case,  how- 
ever, the-  current  must  be  kept  down  to  the  proper  amount 
bv~a  water  rheostat. 


HIGH  FREQUENCY  ELECTRICITY 


29 


CHAPTER  II. 

TRANSMITTING  APPARATUS. 

1.  The  Water  Rheostat. — In  order  to  prevent  too  much 
current  from  flowing  into  the  transformer  when  it  is  being 
used  for  wireless  or  for  high  frequency  work,  it  is  necessary 
to  use  a  water  rheostat  or  an  impedence.  The  water  rheostat 
is  very  much  cheaper  than  the  impedence,  and  it  is  very  use- 
ful and  handy.  With  it  the  amount  of  current  can  be  regulated 
easily  and  minutely ;  and,  since  the  amount  of  current  has 
much  to  do  with  the  tuning,  as  we  shall  show  later,  it  is  im- 
portant to  be  able  to  regulate  it  very  closely. 

With  666  turns  in  the  primary,  the  rheostat  is  not  nec- 
essary, but,  as  the  turns  are  cut  out  to  secure  higher  voltages, 
it  becomes  necessary. 

t  Obtain  a  glass  battery  jar  or  a  glazed  crock,  holding  about 
a  gallon  of  water.  See  Fig.  14  for  details  of  construction. 
Cut  two  pieces  of  galvanized  iron,  G  and  Q,  to  fit  in  the  jar, 
making  Q  a  little  smaller  than  G.  To  G  solder  a  number  12 
rubber  covered  copper  wire,  and  attach  it  to  the  binding  post 


Fig.  14.     Water  rheostat. 

G  and  Q,  galvanized  iron  plates;  J,  glass  battery  jar  or  crock; 
A,  rubber  covered  lead  to  G;  R,  brass  rod;  S,  thumb  screw;  H,  brass 
bearing;  T,  B,  binding  posts. 


30  WIRELESS  TELEGRAPHY  AND 

B.     Prepare  a  wooden  cover  for  the  jar  on  which  the  binding 
posts  T  and  B,  and  the  brass  bearing  H  are  placed. 

Solder  a  brass  rod  one-eighth  of  an  inch  in  diameter  to  the 
galvanized  iron  plate  Q.  Prepare  a  brass  bearing  H  with  a 
thumb  screw  S,  so  that  the  rod  R  can  slide  freely  in  H,  and 
fasten  in  any  position  by  tightening  the  thumb  screw  5". 
Connect  the  binding  post  T  and  the  brass  bearing  H  by  a 
number  12  copper,  rubber  insulated  wire.  Solder  the  connec- 
tions. If  this  jar  be  nearly  filled  with  water  in  which  a  little 
salt  is  dissolved,  it  makes  an  excellent  rheostat. 

2.  The  Impedence. — Instead  of  a  water  rheostat,  an  im- 
pedence  may  be  employed.  The  impedence  is  more  econom- 
ical, as  the  current  is  choked  back  by  the  inductance,  or  back 
electromotive  force  of  inductance.  The  water  offers  a  resist- 
ance and  is  heated  by  the  current.  This  heating  consumes 
energy.  The  impedence  is  made  on  the  same  principle  as. the 
transformer,  without  any  secondary. 

Proceed  to  build  the  impedence  as  directed  for  the  pri- 
mary of  the  transformer  in  Figs,  i,  2,  j  and  4.  They  need  not 
be  so  heavily  insulated,  however.  No  empire  cloth  need  be 
used. 

Cover  the  iron  core  pretty  heavily  with  tape.  Wind  on 
the  form  as  described,  putting  a  layer  of  paraffined  paper  be- 
tween each  layer.  Instead  of  making  the  coils  as  long  as  the 
core,  make  them  only  half  as  long  and  bring  out  taps  every 
fifty  turns.  It  would  be  better  still  to  bring  them  out  every 
twenty-five  turns. 

The  coils  should  then  be  made  one-fourth  as  long  as  the 
core.  Each  coil  should  be  thoroughly  taped  with  cotton  tape. 
They  should  be  assembled  on  the  core  with  fullerboard  be- 
tween each  coil  and  connected  in  series.  Join  the  inside  of  one 
coil  to  the  outside  of  the  following  one,  and  see  to  it  that  the 
turns  continue  on  around  the  coil  in  the  same  direction. 

If  coils  are  put  on  both  legs  of  the  core,  the  coils  on  one 
leg  should  go  around  the  iron  in  the  opposite  direction  to 
those  on  the  other  leg,  the  same  as  they  go  on  an  electro- 
magnet. 


HIGH  FREQUENCY  ELECTRICITY  31 

Bring  the  taps  out  to  a  rheostat  on  the  cover  as  de- 
scribed for  Fig.  /j.  In  this  case,  however,  there  would  be 
more  points.  Imbed  the  impedence  in  oil  or  wax.  The  wire 
should  be  the  same  size  as  the  wire  in  the  primary  of  the 
transformer  with  which  it  is  to  be  used.  It  is  better  to  use 
double  cotton  covered  wire  for  the  impedence.  In  case  the 
impedence  is  to  be  used,  the  transformer  need  have  but  200 
turns  or  less  in  the  primary.  The  impedence  itself  should 
have  at  least  250  turns. 

The  water  rheostat  is  a  very  handy  piece  of  apparatus 
and  much  cheaper  than  the  impedence. 

3.  The  Condenser. — In  order  to  accumulate  the  electricity 
and  discharge  it  across  an  air  gap,  in  order  to  set  up  electric 
oscillations,  a  condenser  is  necessary.  Procure  16  or  20  plates 
of  common  window  glass,  8  by  10  inches.  Obtain  a  couple 
of  pounds  of  lead  or  tin  foil,  such  as  is  sold  by  seed  merchants. 

Shellac  the  tin  foil  on  to  both  sides  of  the  glass  plates, 
leaving  about  one  inch  margin  on  each  side,  if  the  voltage  is 
about  10,000. 

If  the  voltage  of  the  transformer  is  20,000,  leave  a  two- 
inch  margin  on  three  sides,  and  a  three-inch  margin  on  the 
fourth  side.  In  order  to  shellac  the  tin  foil  on  the  plates 
easily,  the  following  method  should  be  pursued.  Either  buy 
the  shellac  already  mixed  or  put  orange  shellac  in  alcohol  and 
allow  it  to  dissolve. 

Fill  a  quart  bottle  One-quarter  full  of  the  dry  shellac,  and 
then  fill  the  bottle  with  wood  alcohol.  Allow  it  to  stand 
twenty-four  hours.  Shake  well  and  dilute  with  alcohol  until 
it  is  very  thin.  Cut  the  tin  foil  to  the  proper  size.  With  an 
ordinary  paint  brush,  paint  the  glass  with  the  shellac,  and 
immediately  apply  the  tin  foil,  painting  the  surface  over  with 
the  shellac. 

Have  at  hand  a  hard  rubber  roller,  such  as  is  used  by 
photographers  in  rolling  down  photographs  upon  cardboard 
when  mounting  them.  Keep  the  roller  moist  with  the  shellac, 
and  proceed  to  roll  down  the  tin  foil  until  it  fits  smoothly. 


32 


WIRELESS  TELEGRAPHY  AND 


If  the  roller  is  not  kept  moist  by  dipping-  in  the  shellac,  the  tin 
foil  adheres  to  it  instead  of  the  glass. 


Fig-  75  gives  the  details  of  the  condenser,  and  Fig.  16  is 
a  photograph  of  it.  Cut  two  boards  D  for  an  upper  and  a 
lower  base. 


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Fig.   15.     Condenser. 

Xail  cleats  K  on  the  lower  base  to  serve  as  legs  and 
to  keep  it  from  warping.  Provide  strips  of  wood  C,  an  eighth 
of  an  inch  wide  and  10  inches  long.  Xail  them  on  the  upper 
and  lower  bases,  parallel  to  the  12-inch  edge.  They  should  be 
far  enough  apart  so  that  the  glass  plates  can  easily  slide  in  the 
grooves  H. 

Take  four  posts  S,  8  inches  long  and  \l/2  inches  square. 
They  should  be  long  enough  to  allow  the  plates  to  slide  in 
easily  between  the  upper  and  lower  bases  D.  Screw  or  bolt 
the  top  and  bottom  to  these  posts,  putting  the  posts  at  the 
four  corners.  The  bolts  are  here  shown  going  through  from 
the  top  to  the  bottom. 

If  screws  are  used,  eight  strips  of  wood,  y%  of  an  inch 
thick,  \l/2  inches  wide  and  10 j4  inches  long,  should  be  nailed 
on  each  post,  being  also  nailed  to  the  upper  and  lower  bases 
in  order  to  make  the  frame  strong.  Obtain  brass  pieces  F, 
10  inches  long  and  J4  uich  square.  Drill  holes  in  the  brass 
and  screw  them  on  to  the  posts  on  the  same  side  of  the  con- 
denser, as  shown  in  the  photograph  and  cut. 


HIGH  FREQUENCY  ELECTRICITY  33 

In  the  upper  brass  strip,  the  holes  should  be  drilled  di- 
rectly opposite  alternate  spaces  between  the  plates.  In  the 
lower  brass  strip  the  holes  should  be  opposite  alternate  spaces, 
but  not  opposite  the  same  spaces  as  in  the  upper  brass  piece. 

Instead  of  the  brass  strips  F,  a  helix  of  brass  wire  can  be 
used.  Place  wooden  strips  in  place  of  the  brass  strips.  Upon 
the  wooden  strips  fix  the  wire  helix. 


Fig.  16.     Condenser,  showing  brass  contact  piece  on  top. 

Obtain  sixteen  pieces  of  spring  brass  wire  large  enough 
to  slide  into  the  holes  just  drilled.  Cut  this  wire  into  lengths 
about  five  inches  long.  From  thin  spring  sheet  brass  cut  strips 
an  inch  wide  and  four  inches  long.  Double  these  strips  into 
springy  loops,  bringing  the  ends  together. 

Punch  a  hole  through  the  doubled  strips  near  the  end 
and  insert  one  end  of  the  five-inch  brass  wires.  With  pliers 
bend  over  the  end  and  pinch  it  down  tightly.  Solder  in  place. 


34 


WIRELESS  TELEGRAPHY  AND 


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HIGH  FREQUENCY  ELECTRICITY 


35 


One  of  these  completed  contacts  is  shown  on  top  of  the  con- 
denser in  Fig.  16. 

Push  the  prepared  strips  into  every  other  space  between 
the  glass  plates  above  and  below,  fitting  the  wires  into  the 
holes  already  prepared.  Put  two  binding  posts  on  each  brass 
strip,  as  shown  in  the  photograph,  in  Fig.  16. 

Fig.  17  shows  clearly  the  arrangement  of  the  clips.  A 
and  B  are  the  brass  strips,  C  the  glass  plates,  and  D  and  E 
the  spring  contacts  in  position. 

This  is  a  top  view  and  shows  them  cvoming  out  on  op- 
posite sides  instead  of  out  on  the  same  side,  as  shown  in  the 
cut  and  photograph.  When  it  is  desirable  to  cut  out  a 
plate,  merely  pull  a  wire  out  of  the  hole  and  "push  it  up  or 
down  out  of  the  way. 


Fig.   17.     Method  of  arranging  spring  contacts  in  condenser. 


Instead  of  boring  holes  in  the  brass  strips,  phosphor 
bronze  clips  can  be  soldered  on  to  the  strips  opposite  every 
other  hole.  The  brass  wires  can  then  be  pushed  down  into  the 
clips  or  be  easily  pulled  out.  The  clips  are  much  handier  than 
the  holes. 

A  wire  helix  is  handier  still,  as  the  brass  rod  can  be  easily 
pushed  into  the  helix  or  pulled  out.  This  is  similar  to  the  lead 
pencil  holder  made  of  a  helix  of  wire. 

4.  The  Spark  Gap. — A  spark  gap,  through  which  the 
charged  condenser  can  discharge,  is  necessary  in  order  to  set 
up  the  oscillations  in  the  aerial.  See  Fig.  18  for  the  details. 


36  WIRELESS  TELEGRAPHY  AND 

Upon  a  base  board  8  inches  long  and  $l/2  inches  wide,  mount 
two  binding  posts  C. 

Prepare  two  standards  A,  out  of  brass,  about  three  inches 
high.  Bore  holes  in  the  upper  part  of  these  posts,  large  enough 
to  admit  the  zinc  or  aluminum  electrodes  B.  These  electrodes 
can  be  made  of  battery  zincs.  The  aluminum  is  better  than 
the  zinc,  but  the  zinc  is  very  good. 

Make  two  set  screws  S  for  clamping  the  electrodes  in 
place.  Connect  the  binding  posts  C  to  the  posts  by  No. 
12  magnet  wire.  The  base  D  can  be  made  of  fiber,  hard  rubber 
or  wood.  The  wood,  however,  should  be  very  dry  or  the  cur- 
rent will  break  across  from  post  to  post  along  the  wood  and 
spoil  the  spark  gap.  The  wood  will  char  and  an  easy  path  is 
formed  for  the  current. 


Fig.    19.      The    anchor    spark    gap. 

5.  The  Anchor  Spark  Gap. — An  anchor  spark  gap  can 
be  made  similar  to  the  one  just  described,  but  smaller.  If 
desired,  one  like  Fig.  19  can  be  constructed  very  easily.  Out 
of  half-inch  hard  rubber  or  fiber,  cut  a  ring  y2  inch  across 
and  \y2  inches  inside  diameter.-  In  this  ring  fit  binding  posts 
P  and  P. 

Bore  holes  large  enough  to  admit  small  zinc  rods  Z. 
Connect  the  electrodes  Z  to  the  binding  posts  P  by  flexible 
lamp  cord  W.  The  rods  Z  can  be  threaded  and  screwed 
through  nuts  fastened  to  the  ring  if  desired. 

This  spark  gap  is  to  be  put  in  series  with  the  aerial.  The 
aerial  should  be  attached  at  P,  and  the  other  terminal  P  should 


HIGH  FREQUENCY  ELECTRICITY 


37 


lead  to  the  sending  helix.  This  serves  to  break  the  connection 
to  the  ground  through  the  sending  helix,  when  the  receiving 
apparatus  is  cut  in. 

6.  The  Sending  Key. — Purchase  an  ordinary  Morse  key. 
Remove  the  points  at  A  and  B,  see  Fig.  20,  and  solder  in  their 
place  two  pieces  of  silver  as  large'  as  dimes.  In  soldering 
them  on,  see  that  their  surfaces  are  flat  and  come  squarely 
together  when  the  key  is  closed.  Fifteen  to  twenty  amperes 
can  be  taken  through  these  contacts  without  any  trouble. 
This  idea  was  suggested  by  Mr.  Dean  Farran  of  the  Poly- 
technic High  School. 


Fig.  20.     The   Morse  telegraph   key. 

If  you  have  a  lathe  and  desire  to  make  your  own  key, 
the  details  are.  shown  in  Fig.  20.  The  binding  post  E  is 
insulated  from  the  base  D,  which  is  made  of  metal,  by  a  hard 
rubber  washer  F.  Platinum  points  can  be  used  instead  of  the 
silver,  but  they  are  expensive  and  the  silver  works  very  well. 


38 


WIRELESS  TELEGRAPHY  AND 


Plate  II. 


Photograph   of   sending   tuning  helix   described   in    Fig.   21 
and  shown  in  Plate  X. 


HIGH  FREQUENCY  ELECTRICITY 


39 


m         m 

Fig.  21.     The  sending  helix. 


7.  The  Sending  Helix. — The  details  of  the  sending  helix 
are  shown  in  Fig.  21.  Cut  out  two  circular  blocks  A  of  dry 
wood,  one  inch  thick  and  one  foot  in  diameter.  Screw  two 
cleats  to  each  to  prevent  them  from  warping.  Prepare  eight 
strips  of  wood  E,  8  inches  long  and  \y±  inches  square. 

Describe  circles  eight  inches  in  diameter  upon  the  upper 
part  of  the  lower  base  and  upon  the  lower  part  of  the  upper 


'  40  WIRELESS  TELEGRAPHY  AND 

base.  Divide  each  circle  into  eight  parts,  and,  with  screws, 
fix  the  posts  in  position  around  the  circle,  as  shown  in  Fig.  21. 

Upon  the  lower J^ase  fix  a  large  binding  post  F,  24  of  an 
inch  high  and  ^  an  inch  in  diameter.  Make  a  brass  strap  H, 
*4  of  an  inch  wide  out  of  brass  l/%  of  an  inch  thick,  having  a 
shank  \y2  inches  long. 

Put  the  strap  around  the  binding  post  and  bolt  it  to  the 
wire  as  shown  at  H  in  the  cut.  Obtain  about  40  feet  of  No. 
5  spring  brass  wire.  This  is  the  wire  to  one  end  of  which  the 
brass  clamp  B  is  bolted.  This  wire  should  be  wound  on  the 
helix,  making  turns  about  24  of  an  inch  apart. 

In  order  to  get  the  distances,  tie  a  string  to  the  binding 
post  and  wrap  it  once  around  the  helix,  letting  the  end  of  it 
be  24  °f  an  inch  above  the  base  of  the  helix.  Mark  on  each 
post  the  place  where  the  string  rests.  Take  the  string  off 
and  with  a  ruler  lay  off  marks  on  each  post,  24  of  an  inch 
apart,  beginning  24  of  an  inch  from  the  first  mark  on  each  post. 

Clamp  the  wire  to  the  post  F,  and  wind  it  on,  letting  it 
follow  the  marks.  It  will  go  on  spirally,  making  from  20  to 
22  turns.  Fasten  the  last  turn  to  a  binding  post  M  or  let  it 
end  without  any  attachment. 

The  wires  can  be  held  in  place  in  several  ways.  Screw 
eyes  can  be  screwed  in  at  each  mark  and  the  wire  can  be 
threaded  through  them.  They  can  also  be  fastened  on  with 
double  pointed  brass  or  steel  tacks. 

Three  lead  wires  from  the  helix  should  be  prepared.  These 
wires  should  be  made  of  heavy  rubber  insulated  lamp  cord. 
The  ends  of  the  wires  can  be  merely  hooked  on  to  the  wires 
•of  the  helix,  but  it  is  best  to  make  phosphor  bronze  clips  to 
which  the  ends  of  the  three  wires  can  be  soldered. 


5 


Fig.  22.     Contact  clip,  made  of  rubber  and  phosphor  bronze. 


HIGH  FREQUENCY  ELECTRICITY  41 

The  clips  can  be  made  as  follows :  Bend  a  piece  of  phos- 
phor bronze  A,  Fig.  22,  back  on  itself  at  C,  making  CO  about 
ll/2  inches  long.  The  strip  should  be  about  ^  of  an  inch 
wide. 

Shape  the  end  A  to  fit  the  wire  on  the  helix,  making  it 
smaller,  however,  so  that  .when  it  is  shoved  on,  it  will  spring 
down  on  the  wire  and  hold  fast.  Over  the  end  C  put  a  hard 
rubber  handle  R,  having  first  soldered  the  wire  W  to  the  end 
C  of  the  bronze  clip.  Put  a  screw  in  at  vS  to  hold  the  bronze 
clip  in  place. 


42  WIRELESS  TELEGRAPHY  AND 

CHAPTER  III. 

% 

THE   AERIAL. 

1.  The  Mast. — A  vertically  or  horizontally  suspended 
conductor,  grounded  at  one  end,  but  otherwise  insulated,  will 
have  a  current  of  electricity  set  up  in  it,  if  cut  by  the  electro- 
magnetic waves  in  the  ether.  This  wire  can  be  stretched  from 
building  to  building  or  between  two  poles,  thus  forming  a 
horizontal  aerial ;  or  it  can  be  suspended  vertically  from  a  pole. 

The  higher  the  aerial  the  better,  but  good  results  can  be 
obtained  frow  low  aerials.  They  should  be  at  least  30  feet 
from  the  ground.  Generally  a  mast  from  60  to  75  feet  can 
be  easily  erected.  The  mast  can  be  raised  directly  from  the 
ground,  or  a  pole  can  be  put  on  top  of  the  house.  It  depends 
entirely  upon  circumstances  whether  the  one  or  the  other 
method  is  used.  Sometimes  a  tree  60  or  70  feet  high  can  be 


Fig.  23.     Method  of  raising  pole. 

obtained.  Such  a  mast  can  be  easily  erected  in  the  following 
manner :  (For  details  see  Fig.  23.}  Dig  a  hole  H  in  the  ground 
about  3  feet  deep.  Slant  one  side  of  the  hole  so  that  the  butt 
M  of  the  pole  comes  against  the  other  side  of  the  hole.  Make 
a  horse  C  about  6  feet  high  and  lift  the  pole  into  the  crotch. 
To  the  middle  of  the  pole  attach  a  block  and  pulley  O. 

Set  a  stake  B  in  the  ground  and  attach  another  block  and 
pulley  to  it.  Lift  the  pole  R,  and  shove  the  horse  C  toward 
the  hole,  at  the  same  time  tightening  the  rope  at  S.  By 
following  this  method,  the  pole  will  finally  drop  into  the  hole. 


HIGH  FREQUENCY  ELECTRICITY 


43 


Fig.  24. 

Insulators. 


2.  Guy  Wires. — Before  *  the  pole  is 
erected,  however,  guy  wires  should  be  at- 
tached to  it,  as  shown  in  Fig.  25.  These 
wires  must  be  thoroughly  insulated  or  they 
will  absorb  the  energy  of  the  electro-mag- 
netic waves  and  conduct  it  to  the  ground  in 
the  form  of  an  electric  current.  Cut  blocks 
of  dry  wood,  A  and  B,  Fig.  24,  8  inches  long 
and  \l/2.  inches  square.  Bore  holes  about  an 
inch  from  the  two  ends  at  C  and  F. 

On  the  adjacent  side  of  the  block  at  E 
and  D,  an  inch  and  a  half  from  the  end,  bore 
holes  at  right  angles  to  the  first  holes.  From 
12  to  18  of  these  will  be  necessary.  Boil 
them  in  hot  paraffine  for  an  hour  or  so, 
until  air  bubbles  cease  to  come  from  them.  They  will  then 
make  fine  insulators. 

Obtain  six  coils  of  galvanized  iron  clothes  line  wire,  three 
of  them  100  feet  long  and  three  of  them  50  feet  long.  Buy 
one  extra  piece  50  feet  long.  This  wire  should  be  stranded 
wire,  about  seven  strands  to  the  wire.  Cut  pieces  from  the 
extra  wire  about  3  feet  long,  and  thread  them  through  the 
holes,  as  shown  in  Fig.  24,  joining  the  two  free  ends  together. 
To  thread  the  wire,  put  one  end  through  one  hole  F.  Put  this 
end  through  the  hole  E,  forming  the  loop  behind  block  A. 
Bring  the  two  free  ends  of  the  wire  together,  forming  the  loop 
EF  in  front  of  the  block  A.  The  two  loops  can  be  made 
of  separate  pieces  of  wire  if  desired.  Through  the  loops  thus 
formed,  the  guy  wires  can  be  placed.  These  form  convenient 
and  excellent  insulators. 

Wire  three  insulators  at  the  top  of  the  pole  and  three 
at  the  middle  of  the  pole,  as  shown  in  Fig.  25,  I.  A  wire 
band  should  be  put  around  the  pole  first.  The  insulator  should 
then  be  wired  to  the  wire  band  by  a  separate  wire.  Have  the 
three  insulators  distributed  equidistant  around  the  pole  at  the 
middle.  Those  at  the  top  should  be  spaced  so  as  to  come 
between  those  in  the  middle,  so  that  the  .  six  insulators  are 
equally  distributed  around  the  pole.  Loop  the  guy  wires  into 


44 


WIRELESS  TELEGRAPHY  AND 


Fig.   25.      Pole   and   guy   wires    connected    to    form   an   aerial. 

the  loops  on  the  insulators,  as  shown  in  Fig.  24  at  H  and  G. 
Wire  a  block  and  pulley  to  the  top  of  the  pole,  and  reeve  a 
rope  through  it  long  enough  to  form  an  endless  rope  to  the 
ground,  the  rope  being  twice  as  long  as  the  pole  is  high. 

When  all  is  ready,  raise  the  pole  as  already  described. 
If  sufficient  help  is  at  hand,  the  pole  can  be  raised  by  having 
three  persons  steady  the  pole  by  holding  the  guy  wires,  while 
two  or  three  others  raise  the  pole.  These  latter  persons  should 
have  long  poles  with  spikes  in  the  ends  of  them.  By  jabbing 
the  spikes  into  the  pole  and  pushing,  the  pole  can  be  raised. 

3.     Dead  Men. — Six  dead  men  to  which  to  attach  the  guys 


HIGH  FREQUENCY  ELECTRICITY 


45 


should  be  prepared  as  follows:  To  a  two-by-four  A,  Fig.  26, 
nail  cross  pieces  B  and  C,  at  right  angles  to  one  another. 

Bury  the  end  on  which  the  cross  pieces  are  nailed  in  the 
ground,  placing  the  dead  men  equal  distances  apart  around 
the  pole,  putting  three  of  them  15  feet  away  from  the  pole, 
and  the  other  three  20  feet  away  from  the  pole.  Fix  wire  loops 
to  the  dead  men  in  the  same  manner  in  which  the  wire  was 
threaded  into  the  insulators  in  Fig.  2^. 

Wire  the  insulators  to  these.  Put  the  lower  ends  of  the 
guy  wires  through  these  loops,  and  tighten  t^em  evenly  all 
around  until  the  pole  is  straight. 

These  insulated  guy  wires  in  themselves  form  an  excellent 
aerial.  If  they  are  connected  together,  as  shown  in  Fig.  25 
at  W ',  and  the  connecting  wires  are  brought  into  the  instru- 
ments, excellent  results  are  obtained.  This  is  true  if  the  guy 


Co 


<0 

s 

I 


Fig.  26.    Dead  men. 


Fig.  27. 


46  WIRELESS  TELEGRAPHY  AND 

wires  are  made  of  galvanized  iron  wire.  Iron  wire  will  not 
do  as  well  for  an  aerial.  It  works,  but  not  nearly  as  well. 

This  pole  can  be  put  up  in  two  or  three  sections.  Put 
up  the  first  section  as  just  directed.  Each  section  should  be 
guyed.  In  order  to  climb  to  the  top  of  the  first  section,  make 
a  ladder  as  shown  in  Fig.  27.  Take  a  one-by-three  as  long  as 
the  section  or  3  feet  shorter.  Nail  cross  pieces  on  it,  made 
of  one-by-threes,  at  intervals  of  lj^  feet.  Stand  this  up  against 
the  section  already  raised.  Let  the  lower  end  rest  on  the 
ground  and  wire  the  bottom  of  it  to  the  pole.  Wire  it  to  the 
pole  at  intervals  of  3  feet,  wiring  it  as  you  climb.  This  makes 
a  solid  and  substantial  thing  to  stand  on  while  working  at  the 
top  of  the  pole.  If  you  have  climbers  and  know  how  to  use 
them,  the  ladder  is  not  necessary. 

To  put  up  the  second  section,  attach  a  block  and  pulley 
to  the  top  of  the  section  already  up.  Raise  the  second  sec- 
tion, with  the  guy  wires  attached  to  it,  against  the  first  sec- 
tion. Put  one  end  of  the  rope  through  the  pulley  and  bring 
it  down,  attaching  it  to  the  bottom  of  the  second  section. 

Put  a  rope  loosely  around  the  two  poles  at  the  top.  Climb 
the  pole  and  have  some  one  pull  on  the  rope,  thus  raising  the 
second  section  vertically  while  you  steady  it.  Three  persons 
should  also  hold  the  guy  wires  as  it  goes  up,  in  order  to 
keep  the  section  from  falling  over.  When  the  section  is  raised 
so  that  it  overlaps  the  first  section  by  2  feet,  wire  it  firmly 
to  the  first  section  and  attach  the  guy  wires  so  as  to  hold 
the  section  straight  in  place. 

If  three  sections  are  to  be  put  up,  the  second  section 
should  be  raised  against  the  first.  Raise  the  third  section 
as  just  described,  and  wire  it  to  the  top  of  the  second.  Then 
raise  the  two  sections  as  described  for  the  raising  of  the  second 
section.  If  the  pole  is  to  be  put  on  a  building,  it  can  be  raised 
in  a  similar  manner  to  the  one  just  described  and  be  guyed  to 
the  house  instead  of  to  dead  men  buried  in  the  ground. 

4.  The  Aerial. — There  are  several  kinds  of  aerials,  but 
they  may  be  divided  into  two  types,  the  vertical  and  the  hori- 
zontal aerials.  In  the  horizontal  aerial,  the  wires  are  stretched 
between  two  masts,  two  buildings  or  two  hills.  One  or  both 


HIGH  FREQUENCY  ELECTRICITY 


47 


ends  may  be  brought  down  to  the  instruments.  If  both  ends 
are  brought  in,  it  is  a  looped  aerial. 

The  vertical  aerial  is  hung  nearly  vertical  from  the  pole. 
It  may  have  the  lower  end  brought  in  to  the  instruments,  or 
it  may  have  the  wires  all  connected  at  the  top,  the  wires  being 
brought  in  to  the  instruments  in  two  groups,  thus  forming 
a  looped  aerial. 

The  higher  these  wires  are  strung,  the  greater  the  dis- 
tance over  which  the  plant  can  be  operated.  The  horizontal 
aerial  is  better  than  the  vertical  one.  The  more  wires  there 
are  and  the  farther  they  are  apart,  the  farther  they  can 
be  made  to  operate,  both  in  receiving  and  sending.  The  wires 
should  be  as  large  as  possible  in  order  to  have  as  little  resist- 
ance as  possible. 


Fig.  28.     General  plan  of  aerial. 

Take  two  pieces  of  dry  wood  A,  Fig.  28,  long  enough  so 
that  the  wires  will  be  about  one  foot  apart.  These  are  called 
spreaders.  In  this  case  we  will  put  in  five  wires.  The  spread- 
ers must  be  about  6  feet  long.  They  should  have  a  cross 
section  of  at  least  1*4  inches  for  a  vertical,  and  \l/2  inches  for 
a  horizontal  aerial.  Bore  five  holes  in  them  a  foot  apart  and 
put  the  wires  through. 

Through  the  ends  of  the  spreaders  A,  bore  holes  and  in- 
sert a  stout  rope  E.  Insulators  described  in  Fig.  24  should 
be  attached  at  /.  Stretch  the  aerial  horizontally  along  the 
ground  and  put  on  additional  spreaders  C  and  Q  to  keep  the 
wires  apart.  The  number  of  these  necessary  depends  on  the 
length  of  the  aerial.  They  may  be  made  of  wood  or  wire. 

At  the  other  free  end  of  the  aerial,  attach  a  long  rope 


48 


WIRELESS  TELEGRAPHY  AND 


to  the  insulator.  Solder  all  of  the  wires  of  the  aerial  together 
at  the  lower  end,  and  solder  on  a  leading-in  wire. 

It  is  better,  however,  to  bring  all  of  the  wires  down  to  the 
instruments.  In  this  case  each  one  of  the  wires  of  the  aerial, 
shown  in  Fig.  28,  should  be  brought  down  and  twisted  to- 
gether into  a  cable.  The  cable  is  then  brought  in  to  the  in- 
struments. This  is  very  much  better,  as  the  resistance  of  the 
aerial  is  very  much  lessened.  Form  a  knot  in  the  endless  rope 
that  runs  through  the  pulley  at  the  top  of  the  pole,  and  tie 
the  insulator  at  the  upper  end  of  the  aerial  to  the  knot. 

When  all  is  ready,  pull  the  aerial  up  into  position.  Tie 
the  rope  at  the  lower  end  of  the  aerial  to  a  dead  man,  pulling 
the  rope  taut.  Conduct  the  leading-in  wires  in  to  the  instru- 
ments, carrying  them  through  porcelain  insulators  set  in  the 
walls  or  windows. 

5.  Types  of  Aerials. — Figs.  29  and  30  give  different  types 
of  simple  aerials.  The  methods  of  connection  to  the  instru- 
ments are  given  in  Figs,  31,  32,  45,  50,  51,-  5^,  53  and  59. 
Figs.  31,  32  and  59  show  the  method  for  looped  aerials,  59 
being  the  best.  D  is  the  detector.  In  the  simplest  case,  the 
lower  end  of  the  aerial  is  brought  to  one  terminal  of  the 


Fig.  29.     Method  of  grouping  wires  in  aerial. 


HIGH  FREQUENCY  ELECTRICITY 


49 


detector  and  the  other  side  of  the  detector  is  grounded,  a,  b 
and  c,  Fig.  29,  show  different  methods  of  grouping  the  wires. 
In  a  they  are  all  connected  together  in  parallel,  and  one  lead 
wire  is  used.  This  wire  should  be  as  large  as  possible.  If  the 
wire  is  made  of  many  strands  of  small  wire,  it  is  better  than 
one  large  wire.  In  b  the  aerial  is  divided  into  two  groups, 
and  in  c  the  top  of  the  aerial  is  brought  in  to  the  instruments 
as  well  as  the  lower  end. 

Fig.  30  is  an  example  of  a  fan-shaped  aerial. 


Fig.  30.     Fan-shaped  aerial. 

The  wires  are  all  connected  together  at  the  top  and 
brought  down,  spread  out  in  the  shape  of  a  fan.  The  wires 
are  about  6  inches  apart  at  the  top  at  K.  R  and  .S  are  ropes 
attached  to  an  insulator  at  N.  EGHF  is  a  wire  connecting  the 
wires  together  at  the  lower  end.  From  E  to  G  and  G  to  H 
is  about  5  feet,  etc.  The  further  they  are  apart  the  better. 
This  distance  will,  of  course,  depend  upon  the  space  at  one's 
disposal.  B  and  A  are  insulators  and  D  and  C  are  dead  men. 


50 


WIRELESS  TELEGRAPHY  AND 


One  wire  may  be  attached  to  EF  and  be  brought  in  to 
the  instruments  or  a  wire  may  be  brought  in  from  each  wire 
of  the  aerial,  being  formed  into  a  strand  before  being  taken  in. 

If  this  group  of  wires  faces  south,  another  group  similar 
to  this,  but  facing  east  or  west,  will  greatly  add  to  the  power 
of  the  station.  If  the  waves  come  in  edgewise  to  the  aerial, 
the  effect  is  not  as  good.  In  fact,  an  umbrella  aerial  is  about 
the  best  thing  in  the  line  of  vertical  aerials. 

Put  in  dead  men,  as  indicated  in  Fig.  25.  Bring  down 
from  the  top  of  the  pole  as  many  wires  as  you  desire.  The 
wires  should  be  attached  in  the  same  manner  as  the  guy  wires 
are  attached,  and  all  should  be  connected  together  at  the  top, 
the  guy  wires,  of  course,  forming  a  part  of  the  combination. 

Using  the  guy  wires  about  10^  feet  from  the  ground  as 
fixed  points,  run  a  large  wire  around,  connecting  the  guy 
wires  10  or  15  feet  from  the  ground.  Attach  the  lower  ends  of 


Fig.  32.  Looped  aerial, 
Shoemaker  system,  show- 
ing aerial  as  part  of  closed 
oscillation  circuit. 


Fig.  31.     Looped  aerial,  showing  different  arrangement. 
BDC,  closed  oscillation  circuit;  B,  tuning  coil;  D,  detector;  C,  con- 
denser; G,  ground;  A,  aerial;  E,  static  tuning  coil. 


HIGH  FREQUENCY  ELECTRICITY  51 

the  other  wires  to  it.  This  secures  a  large  capacity  with 
equal  surfaces  exposed  in  all  directions,  so  that  the  aerial 
can  receive  and  radiate  as  strongly  in  one  direction  as  in 
another. 

Experiment  indicates  that  the  waves  can  be  directed  to  a 
greater  or  less  degree. 

If  the  aerial  is  horizontal,  the  waves  are  radiated  more 
strongly  in  the  direction  in  which  the  aerial  points,  and  the 
radiations  from  the  end  where  the  instruments  are  located  are 
stronger  than  from  the  other  end. 

The  horizontal  aerial  is  an  excellent  type,  since  it  can 
be  easily  looped.  Figs.  51  and  32  are  examples  of  looped 
aerials.  The  loop  A,  Fig.  ji,  may  be  horizontal  or  vertical. 
The  two  leads  are  brought  in  to  the  instruments.  One  is 
connected  through  a  variable  inductance  E  to  the  ground. 

The  other  end  is  connected  to  a  closed  oscillation  circuit 
BDC,  the  junction  of  the  inductance  B  and  the  condenser  C 
being  grounded  at  G.  D  is  the  detector  across  which  a  tele- 
phone is  shunted.  This  is  an  excellent  combination  for  short 
waves.  Fig.  32  gives  the  Shoemaker  system  of  looped  aerial. 
This  connection  is  excellent  for  both  long  and  short  waves. 
Four  adjustable  contacts  are  shown. 

The  horizontal  portion  A  of  the  looped  aerial  should  be 
as  long  as  possible  and  composed  of  as  many  wires  as  it  is 
possible  to  string  up.  The  greater  the  number  of  wires,  the 
greater  the  capacity  and  the  greater  the  power  of  the  station. 

The  wires  are  grouped  into  two  sets,  connected  at  the  top. 
The  two  groups  should  be  as  far  apart  as  possible. 

In  general,  the  higher  the  aerial,  the  greater  the  number 
of  wires  in  it,  the  farther  they  are  apart,  and  the  longer  the 
horizontal  part,  the  greater  the  power  of  the  station. 

Instead  of  making  the  aerial  of  galvanized  iron  wire,  it 
can  be  made  of  copper  or  aluminum  wire.  Stranded  wire  is 
better  than  large  single  wire.  No.  12  aluminum,  however, 
makes  an  excellent  aerial.  Copper  wire  is  excellent  on  account 
of  its  low  resistance,  but  it  stretches  very  easily.  Prosphor 
bronze  wire  is  excellent.  It  does  not  corrode  easily,  possesses 
great  tensile  strength  and  its  conductivity  is  good. 


52  WIRELESS  TELEGRAPHY  AND 

It  is  more  expensive  than  aluminum  and  is  more  dif- 
ficult to  obtain. 

6.  The  Ground. — The  ground  for  the  aerial  should  be  a 
good  one.  Water  pipes  will  do,  but  it  is  better  to  sink  sheets 
of  zinc,  copper  or  galvanized  iron  deep  into  moist  ground. 
Zinc  and  copper  are  rather  expensive,  and  as  galvanized  iron 
is  all  right,  it  is  best  to  use  it.  Dig  a  hole  in  the  ground 
as  deep  as  possible ;  3  feet  is  sufficient,  but  6  feet  is  better. 

It  is  handy  to  dig  the  hole  in  the  shape  of  a  trench  long 
enough  to  enable  one  to  work  in  it  comfortably. 

The  sheets  of  galvanized  iron  should  be  at  least  2x3 
feet.  The  larger  they  are,  the  better,  however.  Solder  No. 
12  or  No.  10  wire  on  to  the  sheets,  and  bury r  them  in  the 
trench,  placing  them  flat  on  the  bottom,  or  edgewise  in  the 
trench.  Lead  the  ground  wire  in  to  the  instruments. 

Keep  the  trench  moist  all  the  time  by  running  water  into 
it  from  the  hose. 


HIGH  FREQUENCY  ELECTRICITY  53 


CHAPTER  IV. 

RECEIVING    INSTRUMENTS. 

1.  The  Detector. — Various  names  have  been  given  to  the 
devices  which  render  audible  the  oscillations  taking  place  in  an 
aerial. 

The  term  detector  covers  them  all.  Cymoscope  is  used 
by  Flemming  in  the  same  sense.  The  term  microphone  applies 
only  to  those  classes  of  detectors  that  depend  upon  the  light 
contact  of  conductors,  giving  a  variable  resistance.  A  great 
many  kinds  of  cymoscopes  have  been  invented,  but  only  those 
that  are  the  most  practical  and  easiest  to  use  will  be  described 
here. 

If  the  contact  between  two  dissimilar  metals  be  oxidized, 
the  resistance  at  the  point  of  contact  is  considerable.  If  this 
contact  be  placed  in  an  oscillation  circuit,  the  voltage  at  the 
point  of  contact,  due  to  the  current  in  the  aerial,  rises  to  a 
value  such  as  to  break  down  the  resistance  and  the  current 
flows.  The  potentiometer  is  adjusted  until  the  voltage  of  the 
local  battery  just  fails  to  break  down  the  resistance. 

The  simplest  microphone  is  formed  by  placing  a  needle 
across  two  pieces  of  electric  light  carbon.  The  carbons  should 
be  brought  to  a  sharp  edge  and  the  needle  laid  across  the 
edges. 

The  carbons  can  be  held  in  metal  clips,  connected  to 
binding  posts.  A  telephone,  a  battery  and  a  potentiometer 
should  be  shunted  around  the  detector,  as  shown  in  Fig.  55. 

This,  however,  is  a  very  troublesome  and  imperfect  piece 
of  apparatus.  An  excellent  detector  can  be  formed  in  the  fol- 
lowing manner :  In  Fig.  33,  A  is  a  piece  of  fiber  or  rubber 
2  inches  square  and  T/2  inch  thick.  Place  two  binding 
posts  Bi  and  B2  upon  this  base,  as  shown  in  the  cut.  Take  a 
piece  of  flat  brass  C,  l/2  inch  wide  and  Vie  inch  thick.  Bend 
this  into  the  form  of  a  letter  "S,"  making  one  flange  Fi 
Y^  inch  long,  and  the  other  flange  F 2,  %  inch  long. 


54 


WIRELESS  TELEGRAPHY  AND 


Plate   III.     Oudin   resonator,  showing  spray   discharge   around  upper 
edge  and  around  ball  terminal. 


HIGH  FREQUENCY  ELECTRICITY 

NH 


55 


jz-  brat!  lubmg 


" — - 

vj 


Fig.   33.     Detector   holder   for   crystal   detectors. 


Bore  a  hole  in  the  flange  Fi  and  fasten  it  to  the  base  be- 
tween the  two  binding  posts  with  a  machine  screw.  The 
binding  post  Bs  does  not  rest  on  the  flange.  Connect  the 
binding  post  Bi  to  the  quarter-inch  flange  by  means  of  a 
wire,  as  shown  in  the  cut.  All  joints  should  be  soldered. 
The  binding  post  Bi  can  be  put  right  on  the  flange  instead  of 
using  the  machine  screw  if  desired. 

Obtain  a  brass  rod  l/>  inch  in  diameter,  and  saw  off  a 
piece  l/2  inch  long,  to  form  the  bearing  R.  Through  the 
center  of  this  bore  a  hole  %  inch  in  diameter.  Solder 
this  on  to  the  end  of  the  flange  Fs  as  shown,  and  drill  a 
hole  in  the  flange  of  the  same  size  of  that  in  the  piece  R. 

Into  the  side  of  R  fit  a  thumb  screw  T.  Obtain  a  brass 
tube  D,  13/4  inches  long  and  large  enough  to  slip  easily  into 
the  hole  in  R.  Thread  this  at  the  upper  end  to  take  a  screw 
F,  upon  which  is  fitted  a  milled  head  H. 

Obtain  a  brass  or  steel  rod  E  to  fit  the  inside  of  the 
tube  D.  The  rod  E  is  loose  and  is  not  threaded.  This  should 
be  long  enough  to  reach  from  the  end  of  the  screw  F  to  the 
metal  plate  P.  The  screw  F  should  be  pointed  so  as  to  bear 
on  the  top  of  E  with  the  least  friction.  E  should  be  pointed 
at  its  lower  end.  Immediately  under  this  fix  a  brass  plate 
P  and  connect  it  to  the  binding  post  Bi  by  a  wire. 

Cut    out    a    ring    G.  of    brass    ^J    inch    in    diameter.      In 


56 


WIRELESS  TELEGRAPHY  AND 


the  center  of  this  place  a  piece  of  carborundum  or  other  ma- 
terial to  be  used  as  a  detector.  Melt  some  solder  and  flow 
it  in  around  it  in  order  to  hold  it  in  place.  Insert  this  under 
the  metal  point  of  the  rod  E.  The  rod  E  can  be  made  shorter 
and  be  fastened  to  F  by  a  spring  if  desired,  so  that  the  pres- 
sure upon  the  carborundum  can  be  regulated. 

Instead  of  soldering  the  carborundum  in  the  ring,  three 
screws  120  degrees  apart  can  be  fitted  into  the  ring  G  so  as 
to  bite  the  carborundum  when  screwed  toward  one  another. 
This  is  very  convenient,  as  any  material  to  be  tested  can  be 
thrust  in  and  held  in  place.  This  forms  a  very  good  detector, 
but  in  order  to  make  it,  one  must  have  a  lathe. 

A  much  cheaper  and  a  better  detector  may  be  made  in 
the  following  manner :  In  Figs.  34  and  55,  B  and  F  are  binding 
posts  and  D  is  a  brass  plate  connected  by  wire  to  the  binding 
post  B.  A  is  a  phosphor  bronze  strip  made  from  sheet  phos- 
phor bronze.  This  is  connected  to  the  binding  post  B  and  bent 
over  to  rest  on  the  detector  material  C,  held  in  its  brass  cell. 
The  spring  A  can  be  made  to  bear  more  or  less  heavily  upon 
the  material  by  bending  it  more  or  less. 

The  spring  A  could  be  arranged  to  come  out  horizontally 
from  a  post  B  and  an  arm  carrying  a  thumb  screw  above  A 
can  be  fixed  in  place,  in  order  to  make  the  point  of  the  spring 
bear  more  or  less  heavily  upon  C.  Fig.  36  is  a  photograph 
of  this  detector. 


Fig.  34.     Crystal  detector  "holder,  side  view. 


HIGH  FREQUENCY  ELECTRICITY 


57 


The  crystals  of  many  metallic  ores  are  good  detectors. 
Flemming  calls  them. crystal  rectifiers.  They  allow  the  cur- 
rent to  flow  in  one  direction,  but  not  in  the  other,  and  they 
thus  shunt  an  undirectional,  intermittent  current  through  the 
telephone. 

After  some  time  these  crystals  polarize,  and  it  is  necessary 
to  let  them  rest  for  a  while.  They  then  recover.  Conse- 
quently, it  is  best  to  have  a  number  on  hand.  Crystalline  iron 
pyrites  makes  an  excellent  detector.  F.  W.  Braun  of  Los 
Angeles  has  a  supply  on  hand,  which  he  offers  for  sale  in 
small  amounts. 


3 


Fig.  35.     Crystal  detector  holder,  front  view. 

The  perikon  detector  is  made  by  placing  zincite  in  con- 
tact with  chalcopyrite.  It  is  sensitive,  but  polarizes  very  eas- 
ily. While  it  seems  to  be  somewhat  more  sensitive  than  iron 
pyrites,  it  is  not  as  hardy.  Iron  pyrites  does  not  polarize 
easily.  In  fact,  a  high  frequency  discharge,  direct  from  the 
sending  circuit,  can  be  sent  through  the  iron  pyrites  without 
throwing  it  out  of  working  order.  It  works  all  right  for  a 
long  time  before  it  needs  rest. 

Perikon,  on  the  other  hand,  is  polarized  very  easily. 
Unless  it  is  disconnected  from  the  receiving  circuit  when  send- 
ing, it  is  thrown  out  of  adjustment. 

Any  sulphide  or  oxide  is  apt  to  prove  a  good  detector. 
When  metals  are  exposed  to  the  air  they  tarnish  or  rust,  due 


58 


WIRELESS  TELEGRAPHY  AND 


Fig.  36.    Photograph  of  crystal  detector,  detailed  in  34  and  35,  showing 
iron  sulphide  or  iron  pyrites  in  position. 


to  the  oxygen  of  the  air  uniting  with  them.  These  oxides  are 
not  good  conductors  of  electricity,  and  consequently  they  form 
good  detector  contacts. 

Carborundum  makes  a  good  detector.  Silicon  is  still 
better,  but  iron  sulphide  is  better  yet.  This  iron  sulphide 
is  known  popularly  as  "fool's  gold.''  All  varieties  do  not 
work.  It  is  the  bright  crystalline  variety  that  does  the  work. 

The  fact  that  iron  sulphide  works  excellently  under  con- 
siderable pressure,  makes  it  a  very  practical  and  convenient 
ore  to  use  for  this  purpose. 

Ordinary  galena  or  lead  sulphide  also  makes  an  excellent 
detector.  It  is  not  as  good  as  the  iron  sulphide,  but  it  is  a 
good  practical  ore  that  works  under  pressure  and  remains  in 
order  when  once  set  in  place.  The  iron  sulphide  is  excellent 
in  that  respect,  if  the  form  of  detector  holder  is  used  as  shown 
in  Figs.  34  and  35. 

The  iron  sulphide  was.  called  to  my  attention  first  by 
Mr.  A.  E.  Abrams,  of  912  Edgeware  Road,  and  the  form  of 
detector  holder  shown  in  Figs.  34  and  55  was  first  used  by 
Mr.  Roy  Zoll.  This  phosphor  bronze  makes  an  excellent  con- 


HIGH  FREQUENCY  ELECTRICITY  59 

tact  for  the  purpose  of  a  detector.     The  lead  sulphide  was 
brought  to  my  notice  as  a  detector  by  Mr.  Dean  Farran. 

These  metallic  oxides  and  sulphides  when  held  in  con- 
tact with  one  another  make  excellent  detectors.  The  lead 
sulphide  and  iron  sulphide  in  contact  make  an  excellent  com- 
bination, but  none  of  them  are  as  good  as  the  iron  sulphide 
alone. 

All  points  on  the  surface  of  these  oxides  and  sulphides 
do  not  work.  The  point  of  the  phosphor  bronze  should  be 
moved  around  until  a  sensitive  point  is  found.  It  will  not  do 
to  polish  the  iron  sulphide,  as  it  seems  to  destroy  its  sensi- 
tiveness. 

When  two  different  metals  are  brought  into  contact,  a 
difference  of  potential  is  developed,  and  a  current  of  elec- 
tricity flows  when  the  circuit  is  completed.  The  current  is 
very  weak,  however,  and  the  difference  of  potential  very 
small.  If  an  oxide  of  the  metal  is  present,  the  voltage  is  not 
enough  to  break  down  the  resistance. 

When  the  current  comes  down  the  aerial,  the  voltage  is 
just  sufficient  to  break  down  the  resistance  of  the  oxide.  A 
current  then  flows  and  a  buzz  is  heard  in  the  telephone. 
These  detectors  are  practical  because  they  are  delicate  and 
reliable.  They  do  not  get  out  of  order  easily  and  they  are 
cheap. 

The  electrolytic  detector  is  very  sensitive  and  popular  for 
long  distance  work.  It  is  extremely  sensitive  and  easily  put 
out  of  order.  The  Walloston  wire  burns  out  continually,  mak- 
ing careful  and  continual  adjustment  necessary. 

They  can  be  made  in  the  following  manner: 

This  is  made  in  a  manner  exactly  similar  to  the  detector 
described  in  Fig.  33,  except  that  the  brass  plate  P  is  left 
off  and  in  its  place  is  substituted  a  glass  carbon  or  platinum 
thimble,  shown  in  Fig.  37  as  6. 

In  order  to  make  this  thimble,  take  a  test  tube  or  other 
glass  tube  and  soften  it  in  the  flame  of  a  bunsen  burner  about 
half  an  inch  from  the  end.  Draw  it  out  and  seal  it  off. 

Keep  it  warm  in  the  flame  and  thrust  a  piece  of  platinum 
wire  through  the  soft  glass,  until  a  small  portion  P,  Fig.  37, 


60 


WIRELESS  TELEGRAPHY  AND 


brass 


Fig.  37.     Electrolytic  detector,  showing  side  and  rear  view. 

sticks  through.  The  base  should  be  rounded  and  somewhat 
flattened  in  the  flame.  Close  the  air  hole  of  the  bunsen 
•burner  and  cool  the  thimble  in  the  flame,  allowing  it  to 
become  covered  with  soot.  Turn  the  flame  down  and  cool 
it  a  little  more  in  the  flame.  This  anneals  the  glass  so  that 
it  is  not  brittle. 

Round  out  a  hole  in  the  base  2,  Fig.  37,  for  this  to  fit 
into.  Solder  a  copper  wire  to  the  platinum  wire  and  carry 
it  to  a  binding  post.  Attach  the  other  binding  post  to  the 
S-shaped  brass  arm.  The  thread  of  the  screw  C  should  be 
very  fine.  Solder  on  to  the  end  of  the  screw  C  a  small  piece 
of  Walloston  wire  W .  Put  a  10  per  cent  solution  of  nitric 


To  Binding  Posl 


Fig.  38.     Electrolytic  detector. 


HIGH  FREQUENCY  ELECTRICITY  61 

acid  into  the  cup.  It  requires  considerable  skill  to  make  this 
detector. 

An  easier  one  to  make  is  shown  in  Fig.  38.  A  is  a  base 
6  inches  long  and  2  inches  wide,  upon  which  are  two  binding 
posts  B,  A  piece  of  brass  vS  similar  to  the  brass  piece  C  in 
Fig-  33  ig  fixed  to  the  base  at  the  end,  opposite  the  binding 
posts  B. 

A  thumb  screw  /,  threaded  to  a  nut  H,  has  its  end  rest- 
ing on  a  lever  L,  pivoted  at  P  by  a  piece  of  spring  sheet 
phosphor  bronze.  A  spring  V  holds  the  end  N  of  the  lever 
against  the  point  of  the  screw  7.  A  groove  is  sawed  in  S1," 
thus  giving  the  end  of  the  lever  N  free  vertical  play. 

This  lever  is  made  of  brass  4  inches  long  from  the  pivot 
P  to  7.  The  end  PC  is  y^  of  an  inch  long.  The  binding  post 
E  is  1  inch  high.  A  brass  rod  G  slips  in  the  binding  post  E. 
This  rod  can  be  held  in  any  position  by  the  set  screw  F. 

The  set  screw  C  is  l/2  inch  long.  To  its  end  is  soldered  a 
Walloston  wire  W.  D  is  a  carbon  cup,  %  of  an  inch  deep. 
Fit  a  band  of  phosphor  bronze  R  tightly  around  this  cup  and 
solder  it  to  the  binding  post  B.  From  the  binding  post  E, 
conduct  a  wire  to  the  other  binding  post  B.  Put  a  10  per  cent 
solution  of  nitric  acid  in  the  cup.  The'  carbon  cup  can  be 
obtained  of  dealers  in  wireless  apparatus  or  one  can  be  made 
from  an  ordinary  electric  light  carbon. 

The  latter,  however,  is  very  porous  and  one  has  to  keep 
rilling  it  constantly.  The  acid  can  be  put  in  with  a  pipette, 
such  as  is  used  for  filling  fountain  pens.  The  thread  on  7 
should  be  as  fine  as  possible.  When  the  long  arm  of  the  lever 
L  is  moved  by  turning  the  thumb  screw  through  a  distance 
7,  a  distance  of  Vioo  of  an  inch,  the  Walloston  wire  moves  only 
Vie  of  that  distance,  or  Vwoo  of  an  inch. 

The  Walloston  wire  in  this  case  does  not  move  perpen- 
dicularly. By  modifying  this  a  little,  a  still  finer  adjustment 
can  be  obtained,  and  the  Walloston  wire  remains  stationary. 
Instead  of  soldering  the  Walloston  wire  to  C,  obtain  a  glass 
tube  a  little  larger  than  the  brass  rod  C.  Close  the  tube  at 
one  end  in  the  bunsen  flame.  By  means  of  plaster  of  Paris 


62 


WIRELESS  TELEGRAPHY  AND 


cement  the  brass  rod  C  in  to  the  glass  tube.  This  glass  tube 
should  be  long  enough  to  reach  y%  on  an  inch  into  the  liquid. 

Provide  another  post  similar  to  E,  and  arrange  a  plunger 
similar  to  G,  to  which  solder  an  arm  at  right  angles.  To  this 
arm  solder  a  rod  similar  to  C,  and  to  the  end  of  it  solder  the 
Walloston  wire. 

By  means  of  this  the  Walloston  wire  can  be  lowered  into 
the  cup  until  it  just  touches  the  liquid.  Then  by  n\eans  of  the 
thumb  screw  7,  the  water  can  be  raised  or  lowered  around  the 
wire.  If  the  plunger  moves  Ywoo  of  an  inch  into  the  water,  it 
does  not  have  its  surface  moved  through  any  such  distance, 
but  through  a  distance  very  much  smaller. 

By  having  the  glass  tube  small  enough,  an  exceedingly 
fine  adjustment  can  be  obtained. 

2.  The  Tuning  Coil. — The  tuning  coil  can  be  of  various 
lengths  and  diameters.  If  they  are  very  large,  however,  they 
will  not  be  sensitive  enough.  The  change  in  inductance  is 
then  too  large  for  each  change  of  turn  due  to  the  sliding  con- 
tact. A  convenient  form  is  made  as  follows :  Obtain  a  piece 
of  hard  rubber,  fiber  or  dry  wood,  1  foot  to  15  inches  long, 
and  2^4  inches  in  diameter.  The  wooden  piece  should  be 
turned  down  in  the  lathe  to  the  required  size. 


Fig.  39.     Tuning  coil. 

Fig.  39  gives  the  details  of  such  a  coil,  and  Fig.  40  is  a 
photograph  of  the  same  coil.  If  possible,  cut  a  helical  groove 
on  this  cylinder  having  20,  22  or  24  threads  to  the  inch.  In 
this  groove  wind  tightly  No.  20,  22  or  24  bare  copper,  brass 
or  phosphor  bronze  wire. 

Phosphor  bronze  wire  is  the  best,  as  it  makes  excellent 
electrical  contact.  If  you  have  no  lathe,  wind  the  wire  on 


HIGH  FREQUENCY  ELECTRICITY  63 

tightly  and  space  it  as  evenly  as  possible  by  winding  string 
between  the  wires.  The  wires  should  not  touch.  If  the  core 
is  made  of  wood,  it  should  be  boiled  in  paraffine.  Before 
beginning  to  wind,  set  a  screw  in  one  end,  to  which  fasten 
the  wire.  At  the  other  end  fasten  the  end  of  the  wire  to  a 
screw,  and  carry  the  terminals  to  binding  posts  upon  the 
end  supports  C. 

These  ends  should  be  large  enough  to  raise  the  coil  free 
of  the  base,  in  this  case  about  2l/2  inches  square  and  1  inch 
thick.  Before  putting  the  helix  in  position,  it  should  be  thor- 
oughly shellaced.  Screw  the  end  pieces  to  the  base  end,  and 
set  screws  through  the  end  pieces  into  the  ends  of  the  helix. 
If  the  helix  is  made  of  tubing,  put  wooden  plugs  in  the  ends 
of  the  tubes.  The  base  should  be  about  5  inches  wide. 

Take  two  pieces  of  phosphor  bronze  sheet  2  inches  long 
and  1  inch  wide.  Cut  off  on  two  sides  so  as  to  form  a  tri- 
angular piece  S,  Fig.  39,  similar  to  those  shown  in  the  photo- 
graph, Fig.  40.  Prepare  a  block  D,  2l/2  inches  long,  l/2  inch 
wide  and  ^  inch  thick.  Place  this  block  about  an  inch 
from  the  helix  on  the  base  and  parallel  to  the  helix.  On  each 
side  of  the  block  nail  strips  of  wood  W  as  long  as  the  base 
and  as  thick  as  the  block,  forming  a  groove  in  which  the  block 
can  slide  parallel  to  the  helix.  Bend  the  phosphor  bronze  strip 
vS  until  it  makes  good  contact  with  the  helix.  Put  a  similar 
arrangement  on  the  other  side,  thus  forming  two  sliding  con- 
tacts. Solder  flexible  wires  to  the  phosphor  bronze  pieces. 

If  desired,  the  helix  can  be  wound  with  double  cotton 
covered  copper  wire.  In  this  case  wind  the  wire  close  ~  to- 
gether. When  finished  shellac  it.  Allow  it  to  dry  and  then 
shellac  again.  Do  this  several  times.  When  thoroughly  dry, 
scrape  or  file  off  the  insulation  where  the  contact  is  to  run. 
In  the  bare  wire  helix,  the  wire  should  be  sand-papered  where 
the  contacts  are  made.  This  is  cheap  and  easily  made,  but  it 
serves  the  purpose  very  well.  If  desired,  the  coil  can  be 
enclosed  in  a  box.  The  grooves  in  which  the  block  runs  can 
be  made  inside  of  the  box  and  a  rubber  knob  can  be  fastened 
to  the  block,  a  slit  being  made  in  the  box  for  the  knob  to 
slide  in. 


WIRELESS  TELEGRAPHY  AND 


^*  .  *~ 

Fig.  40.     Photograph  of  tuning  coil  shown  in  Fig.  39. 


Instead  of  wooden  slides  as  here  described,  they  can  be 
made  of  brass,  as  shown  in  the  photograph  of  a  receiving  set 
in  Figs.  45  and  46.  In  this  set  a  square  brass  tube  fits  and 
slides  over  a  square  brass  rod,  the  phosphor  bronze  contact 
being  soldered  to  the  square  brass  tube.  A  machine  screw 
has  its  head  soldered  to-  the  square  brass  tube  and  the  rubber 
handle  is  screwed  to  it.  This  makes  a  neat  arrangement.  The 
complete  tuning  set  shown  here  will  be  described  later. 

3.  The  Receiving  Condenser. — The  receiving  condenser 
can  be  made  adjustable  or  non-adjustable.  A  suitable  non- 


T 
J 


r 

li 


C 


H 


I  „ 

^ 

-/I 

«)  ~ 

~Vi  —  Q 

i 

Fig.  41.     Paper  condenser. 


HIGH  FREQUENCY  ELECTRICITY 


65 


adjustable  condenser  can  be  made  in  the  following  manner: 
Cut  good  type-writing  paper  into  pieces  3  inches  square. 
Melt  some  paraffine  and  immerse  the  slips  of  paper  in  the  hot 
paraffine,  until  the  bubbles  of  air  cease  to  come  from  them. 

Cut  strips  of  tin  foil  2  inches  by  3  inches,  and  lay  them 
down  as  shown  in  Fig.  41.  Upon  a  piece  of  the  paraffined 
paper  A,  place  a  strip  of  tin  foil  B.  Over  this  lay  a  strip  of 
paper  D,  and  upon  this  a  strip  of  tin  foil  C,  as  shown  in  the  cut. 

The  two  pieces  of  tin  foil  are  thus  separated  by  paraffined 
paper,  and  their  ends  come  out  on  opposite  sides  of  the  con- 
denser. 

Pile  up  alternate  sheets  in  this  manner  until  sufficient 
number  are  placed  together. 

Place  the  assembled  condenser  F  in  a  vise  or  under  heavy 
weights  in  order  to  make  it  as  solid  as  possible.  If  the  con- 
denser is  loose  it  will  make  the  signals  sound  mushy.  Only 
a  very  few  of  these  sheets  are  required. 

About  ten  plates  make  a  good  condenser.  The  free  ends 
K  and  E  should  be  soldered  to  copper  wires  and  be  brought 
to  binding  posts  H.  With  a  little  practice  this  soldering  can 


£• 

(~ 

f 

' 

<Zi 

*"/ 

U2 

°d 

*t 

Fig.  42.     Connection  for  condenser  rheostat. 


66 


WIRELESS  TELEGRAPHY  AND 


be  easily  done.     It  is  best  to  enclose  this  condenser  in  a  box 
and  surround  it  with  parafBne  chips: 

The  adjustable  condenser  can  be  easily  made  by  making 
four  or  five  of  these  simple  ones  of  two  or  three  sheets  each. 
Assemble  them  as  shown  in  Fig.  42.  The  separate  condensers 
Ci,  €2,  €3  and  €4  can  be  piled  on  top  of  one  another,  provided 
the  wires  and  plates  on  the  side  B  are  separated  from  one 
another  by  paraffined  paper.  On  the  side  A,  solder  the  plates 
all  together.  On  the  side  B  solder  wires -to  each  set.  Bring 
them  out  to  separate  binding  posts  /,  2,  3  and  4.  Connect  the 
side  K  to  a  binding  post  A.  Provide  a  second  binding  post 
B,  and  bring  four  wires  from  it  to  binding  posts  /,  2,  3  and  4. 
By  disconnecting  any  one  of  these  wires,  its  particular  con- 
denser is  cut  out. 

A  convenient  wiper  can  be  made  of  phosphor  bronze. 
Cut  a  triangular  piece  of  phosphor  bronze,  one  angle  being  at 
B  and  the  other  two  angles  at  M  and  N.  Of  this  make  a 
rheostat  similar  to  the  one  in  Fig.  13,  except  that  the  wiper 
W  is  a  large  triangular  piece  made  to  cover  all  the  points 
when  all  of  the  plates  are  cut  in.  With  a  swivel  joint  at  B 
and  a  hard  rubber  thumb  piece,  the  wiper  can  be  made  to 
include  as  many  or  as  few  of  the  plates  as  are  desired. 
c 


PL,*, 

a 

E 

'•ff/jo/r 

\ 

/ 

^p 

A 

^ 

1 

e-X 

'    \  >  1       \ 

__^^_^       •—  ~^s_-          -^^^   ••  •        .  —  —  Sfc  ___           ^     ^ 

•O-  ,^>-v-  >  -v_x_  ..—70  -;^2;^r^  —  ^^--^^^rr--^  j>~—  -  —  -  -  -  — 

Fig.  43.      Brass  tube   condenser. 

Fig.  43  shows  a  condenser  made  out  of  brass  tubes  and 
empire  cloth.  Procure  two  brass  tubes  E  and  D,  so  that 
one  can  slip  into  the  other  with  Vie  or  %  of  an  inch  to  spare. 
Make  a  base  A  of  wrood  about  4  inches  wide  and  a  little 
longer  than  the  tubes. 


HIGH  FREQUENCY  ELECTRICITY  67 

Place  binding  posts  c  and  /  on  this  base.  Prepare  two 
end  pieces,  C  and  B,  4  inches  wide  and  3  inches  high.  Around 
the  tube  E  wrap  paraffined  paper  or  empire  cloth,  until  the 
tube  E  with  the  coating  can  slide  easily  into  the  tube  D.  The 
cloth  or  paper  should  be  glued  to  E  and  thoroughly  dried. 

Bore  a  hole  in  the  end  piece  B  just  large  enough  to  receive 
tightly  the  cloth  covered  end  of  the  tube.  Solder  a  wire  to  the 
end  of  E  and  carry  it  to  the  binding  post  c.  A  hole  should 
be  bored  large  enough  in  the  end  piece  C  to  receive  a  collar 
of  brass  M,  this  collar  being  large  enough  on  the  inside  to 
allow  the  tube  D  to  slide  easily,  at  the  same  time  making 
electrical  contact.  Solder  a  wire  to  the  collar  M  and  carry 
it  to  the  binding  post  /.  By  sliding  D  back  and  forth  the 
capacity  of  the  condenser  can  be  easily  varied. 

Instead  of  being  made  to  slide  in  the  collar  M,  the  tube  D 
can  be  made  to  slide  in  the  wooden  end  piece  C  and  a  flexible 
lamp  cord  H  can  be  carried  to  the  binding  post  /.  This  cord 
should  be  long  enough  to  allow  for  the  adjustment  of  the 
slide.  This  makes  a  very  delicate  condenser. 

A  mica  adjustable  condenser  can  be  made  on  the  same 
plan  as  the  paper  one  in  Fig.  38.  Instead  of  tin  foil,  use 
very  thin  copper  sheet  and  instead  of  the  paper  use  very  thin 
mica  sheets.  Glue  or  mucilage  very  thin  paper  on  the  mica 
sheets.  Glue  a  copper  and  a  mica  sheet  together,  allowing 
the  copper  sheet  to  project  over  on  one  side  and  fall  short 
on  the  other,  as  shown  in  Fig.  41. 

These  plates  should  be  about  5  inches  long  and  3  inches 
wide.  Assemble  the  pairs  as  in  the  other  condenser  and  solder 
the  copper  plates  on  each  side  together.  By  pulling  or  push- 
ing on  E  and  K,  Fig.  41,  the  sheets  can  slide  on  one  another 
and  as  much  or  as  little  of  the  plates  can  be  included  as  de- 
sired. This  is  similar  to  the  tubular  condenser  just  described, 
but  of  much  greater  capacity. 

The  whole  should  be  arranged  in  a  box,  and  the  copper 
plates  at  K  should  -be  bolted  to  one  side  of  the  box,  a  wire 
being  led  from  the  bolt  to  a  binding  post.  The  other  side  of 
the  condenser  E  should  have  a  flexible  lamp  cord  soldered 


68  WIRELESS  TELEGRAPHY  AND 

to  it  which  should  be  carried  to  a  binding  post,  the  wire 
being  long  enough  to  allow  of  its  being  adjusted. 

4.  The  Potentiometer. — No  potentiometer  is  needed  with 
silicon,  iron  sulphide  or  lead  sulphide,  as  no  batteries  are  used 
with  these  detectors.  A  potentiometer  can  be  used  to  advan- 
tage with  carborundum,  although  the  carborundum  can  be 
used  without  it. 

Fig.  44  gives  the  details  for  an  adjustable  potentiometer. 
Take  a  block  of  wood  CD  about  11%  inches  long.  Turn  it 
down  in.  the  lathe  so  that  the  part  WE  is  9%  inches  long  and 
2)4 "inches  in  diameter.  Turn  out  notches  TV  %  of  an  inch 
wide,  %  on  an  inch  apart  and  ^4  of  an  mch  deep.  This 
gives  eight  notches,  with  100  ohms  to  the  notch.  If  more 
resistance  is  desired,  make  the  core  longer. 


Fig.  44.     Potentiometer. 

In  these  notches  wind  No.  36  single  silk  covered  copper 
wire.  It  should  be  wound  non-inductively.  In  order  to  do 
this,  wind  off  on  another  spool  about  half  the  wire  needed. 
Put  the  two  spools  of  wire  on  a  shaft  so  that  they  can  unreel 
easily.  Solder  the  free  ends  of  the  wire  together  and  wind 
in  the  notches  until  they  are  nearly  full.  This  gives  about 
100  ohms  to  the  notch.  Two  other  similar  cores  should  be 
prepared,  one  having  10  ohms  to  the  notch  and  the  other 
1  ohm  to  the  notch. 

The  flange  T  should  be  flattened  either  on  the  top  or  side 
and  a  brass  strip  Z  should  be  screwed  to  the  flanges,  two 


HIGH  FREQUENCY  ELECTRICITY  69 

screws  being  set  in  each  flange.     Saw  the  brass  strip  in  two 
over  each  coil,  thus  dividing  it  into  nine  separate  pieces. 

When  each  notch  is  full,  it-  will  be  found  to  have  two 
terminals.  Solder  one  of  these  terminals  to  the  brass  section 
on  one  side,  and  the  other  terminal  to  the  brass  section  on 
the  other  side.  The  coils  are  thus  joined  in  series  through 
the  brass  sections. 

Prepare  end  pieces  C  and  D  3  inches  square.  Make  a  base 
of  wood  6  inches  wide  and  13^  inches  long.  Fasten  the  end 
pieces  C  and  D  on  to  the  core  WE,  and  fasten  the  end  pieces 
to  the  base. 

Make  a  block  P  of  wood  2l/2  inches  long,  ^  inch  wide 
and  y%  inch  thick.  Upon  this  piece  fasten  by  means  of  screws 
a  triangular  contact,  made  of  phosphor  bronze  similar  to  those 
in  Figs.  39  and  40. 

The  tip  should  be  made  large  enough  to  cover  the  spaces 
between  the  brass  pieces  .c.  Put  on  the  wooden  strip  0  so 
that  the  block  P  can  slide  snugly  between  them.  By  bevelling 
the  pieces  0  and  the  slider  P,  it  cannot  come  put  of  the  groove. 

Solder  flexible  lamp  cord  to  the  phosphor  bronze  contact 
piece.  Solder  wires  to  the  brass  end  pieces  and  conduct  them 
to  the  binding  posts  on  the  base. 

If  three  of  these  potentiometers  are  made,  they  can  all 
be  assembled  on  the  same  base.  The  sliding  contact  may  be 
on  the  side,  or  on  top,  as  shown  in  the  photograph  in  Fig.  46. 
The  circuits  for  these  potentiometers  are  shown  in  Figs.  45 
and  55.  Instead  of  wooden  slides  as  here  described,  metal 
slides  can  be  provided  as  shown  in  Fig.  46. 

Fig.  45  is  a  diagram  of  a  complete  oscillation  circuit  com- 
posed of  a  tuning  inductance,  condenser  and  potentiometer 
arranged  on  the  same  base.  B  is  the  tuning  inductance,  P 
the  potentiometer  and  C  the  condenser.  Fig.  46  is  a  photo- 
graph of  the  instrument.  The  condenser  is  inclosed  in  the 
back  part,  the  rheostat  only  being  shown  on  the  cover. 

In  Fig.  45  the  binding  post,  marked  /,  attaches  to  one 
side  of  the  condenser,  marked  R,  to  the  ground,  marked  G,  and 
to  the  lower  rod  of  the  sliding  contact,  marked  D.  The  bind- 


70 


WIRELESS  TELEGRAPHY  AND 


..-A/WWWV. 


Fig.   45.     Connections   for   receiving   set   shown   in    Fig.   46.     8  and   4 
should  be  connected,  although  not  shown  in  the  cut. 

ing  posts  J  and  4  are  attached  to  the  extremities  of  the  poten- 
tiometer P,  and  also  to  the  battery  B. 


Fig.  46.     Photograph   of  tuning  set. 


HIGH  FREQUENCY  ELECTRICITY 


71 


Binding  posts  5  and  6  are  for  the  telephone.  Binding  post 
5  attaches  to  the  sliding  contact  of  the  potentiometer  P,  and 
binding  post  6  attaches  to  binding  post  7  of  the  detector  0. 

Binding  posts  7  and  8  are  for  the  detector.  Binding  post 
8  attaches  to  the  aerial  binding  post  2.  It  should  also  attach 
to  binding  post  4.  This  attachment  is.  not  shown  in  the  cut. 
The  aerial  binding  post  2  also  attaches  to  the  sliding  contact 
B  of  the  tuning  inductance. 

A  photograph  of  this  instrument  is  shown  in  Fig.  46. 
The  button  in  the  upper  right-hand  corner  is  intended  as  a 
detector  switch,  but  the  connections  are  not  shown  in  the  cut. 

This  can  be  connected  up  in  any  other  way  desirable. 
This  connection  here  enables  one  to  include  any  part  of  the 
tuning  inductance  or  as  much  of  it  as  one  wishes  in  the  oscil- 
lation circuit. 


Fig.  47.     Switch  for  changing  from  sending  to  receiving. 

5.  The  Sending  and  Receiving  Switch. — It  is  very  con- 
venient to  be  able  by  one  movement  of  the  hand  to  switch 
from  the  sending  to  the  receiving  apparatus.  When  the  switch 


72  WIRELESS  TELEGRAPHY  AND 

is  thrown  to  the  receiving  position,  it  should  cut  in  the  aerial, 
the  ground  and  the  oscillation  circuit  of'the  receiving  set. 

When  the  switch  is  thrown  to  the  sending  position,  the 
ground  of  the  receiving  side  should  be  broken,  and  the  ground 
on  the  sending  side  should  be  made.  At  the  same  time  the 
detector  circuit  should  be  broken  and  the  aerial  be  switched 
from  receiving  to  sending.  The  arrangement  is  shown  in  de- 
tail in  Fig.  47. 

Take  a  dry,  well  seasoned  board  1  foot  wide  and  2l/2  feet 
long,  and  1  inch  thick.  Place  a  binding  post  B,  2  inches  from 
the  end  X  in  the  middle  of  the  base.  Cut  four  circular  blocks 
Di,  Ds,  D$  and  D^  out  of  fiber,  rubber  or  dry  wood.  These 
should  be  about  3  inches  in  diameter.  Bore  a  1-inch  hole 
through  the  center  of  each,  and  mount  them  on  a  wooden 
rod  L,  16  inches  long  and  1  inch  in  diameter. 

Mount  this  rod  upon  bearings  so  as  to  swing  it  free  of 
the  base.  Place  a  handle  W  on  the  end  of  the  rod,  as  shown 
in  the  cut.  Fasten  a  piece  of  brass  rod  /,  6  inches  long,  ^  mc^ 
wide  and  y§  inch  thick,  upon  the  circular  block  Di.  On  each 
side  of  this  block  and  6  inches  from  it,  arrange  spring  clips 
Fi  and  F2  made  out  of  phosphor  bronze  similar  to  the  contact 
clips  on  the  tuning  coil. 

Place  two  of  them  at  Fi  and  two  of  them  at  F2,  making 
them  shallow,  so  that  the  rod  I  just  makes  good  contact. 
Attach  the  aerial  to  the  binding  post  B.  Bring  a  flexible  lamp 
cord  from  the  binding  post  to  the  brass  piece  /.  By  throwing 
the  switch  to  the  left,  the  aerial  is  connected  to  the  tuning 
coil  E,  and  by  throwing  it  to  the  right  it  is  connected  to  the 
sending  helix  R,  through  the  anchor  gap  5\ 

Put  brass  bolts  through  the  blocks  D2,  Dj  and  04,  at  F, 
H  and  K,  and  on  each  side  arrange  clips  as  shown,  so  that  the 
ends  of  the  bolts  will  be  forced  down  between  the  clips,  thus 
forming  connections  at  these  points.  To  one  of  the  clips  at 
F,  bring  a  lead  from  one  of  the  adjustable  clips  on  the  tuning 
coil,  and  to  the  other  one  of  the  terminals  of  the  detector  D. 

To  the  upper  clip  at  H,  bring  a  wire  from  between  the 
condenser  and  the  tuning  helix.  Attach  the  lower  clip  to  the 
ground  G.  On  the  sending  side,  attach  the  upper  part  of  the 


HIGH  FREQUENCY  ELECTRICITY  73 

sending  helix  to  clip  Fs  through  the  anchor  spark  gap  F2. 
Attach  the  lower  end  of  the  sending  helix  R  to  the  upper  clip 
at  D$.  Attach  the  ground  to  the  lower  clip  at  D$.  At 
04  attach  the  two  terminals  of  the  primary  circuit  as  shown. 
N  is  the  source  of  the  alternating  current,  and  0  is  a  water 
rheostat  for  regulating  the  flow  of  the  current.  Ci  is  the 
condenser,  T  is  the  transformer,  NM  is  the  key  in  the  pri- 
mary circuit  for  sending.  G  is  the  ground,  D  the  detector, 
€2  the  receiving  condenser,  E  the  receiving  tuning  coil  and 
A  is  the  aerial.  Q  is  the  spark  gap. 


74 


WIRELESS  TELEGRAPHY  AND 


CHAPTER  V. 

OPERATION    OF   THE   TRANSFORMER,    SENDING   AND 
RECEIVING   SETS. 

1.  Sending. — The  sending  and  receiving  circuits  are  given 
in  Fig.  47  in  connection  with  the  sending  and  receiving  switch. 
A  circuit  for  sending  is  given  in  Fig.  48. 

i 


Fig.  48.     Sending  circuit,  non-inductive. 

A,  alternator;  R,  water  rheostat;  P,  primary;  S,  secondary;  T, 
transformer;  Ci,  condenser;  Si,  spark  gap;  C,  tuning  helix;  C,  Si,  Ca, 
closed  oscillation  circuit;  IHDEG,  open  oscillation  circuit;  I,  aerial; 
H,  anchor  gap;  D  and  E,  sliding  contacts. 

A  is  the  source  of  the  alternating  current.  K  is  the  key 
for  sending,  and  R  is  a  water  rheostat  or  an  impedence  in 
series  with  the  primary  P  of  the  transformer  T,  the  construc- 
tion of  which  was  worked  out  in  the  previous  pages. 

If  the  transformer  is  a  small  one,  ordinary  lamp  cord  can 
be  used  as  leads  from  R  and  K.  These  leads  should  be  at- 
tached to  an  electric  light  plug  and  the  plug  should  be  screwed 
into  the  ordinary  electric  light  socket.  It  is  also  advisable 
to  have  ..a  switch  in  series  with  the  primary  in  order  to  cut 
the  current  off  entirely  when  not  in  use. 

The  terminals  of  the  condenser  Ci  are  connected  to  the 
terminals  of  the  secondary  of  the  transformer  T.  If  the  key 
K  be  closed,  a  certain  load  is  thrown  upon  the  transformer, 
and  the  condenser  allows  a  current  to  alternate  through  it, 


HIGH  FREQUENCY  ELECTRICITY  75 

depending  upon  the  capacity  of  the  condenser;  the  larger  the 
condenser,  the  greater  the  current  in  the  primary. 

Attach  one  side  of  the  condenser  to  the  lower  part  of  the 
helix  at  C.  Attach  the  other  side  of  the  condenser  to  the 
spark  gap  Si.  From  the  other  side  of  the  spark  gap  lead  a 
wire  to  the  sending  helix,  a  few  turns  above  the  point  C. 

If  the  key  K  be  closed,  the  condenser  draws  a  load  as 
before,  but  when,  the  condenser  is  charged  to  its  full  voltage, 
a  discharge  takes  place  across  the  spark  gap  and  oscillations 
are  set  up  in  the  closed  oscillation  circuit,  consisting  of  Ci, 
Si  and  the  inductance  C. 

If  the  aerial  be  connected  at  D  through  an  anchor  spark 
gap,  and  a  ground  be  attached  to  the  lower  end  of  the  helix 
at  E,  the  open  oscillation  circuit  IHDEG  is  formed  and  a 
minute  spark  passes  across  H. 

With  the  666  turns  of  the  transformer  cut  in,  any  number 
of  amperes  from  l/^  up  to  3^  amperes  can  be  allowed  to  flow 
by  adjusting  the  water  rheostat  R.  If  talking  to  anyone  near 
by,  use  only  *4  ampere.  With  *4  ampere  and  a  60-foot  aerial, 
one  can  easily  work  from  one  to  two  miles,  only  a  tiny  spark 
passing  at  H.  If  it  be  necessary  to  use  more  current  on  ac- 
count of  interference,  or  if  desirable  to  work  to  a  longer  dis- 
tance, cut  in  more  current  by  means  of  the  rheostat. 

When  small  current  is  used,  the  spark  gap  Si  must  be 
very  small.  As  more  current  is  cut  in,  open  the  spark  gap  Si 
so  as  to  keep  a  clear,  even  sounding  spark,  free  from  arcing. 
With  all  the  primary  cut  in,  the  secondary  develops  about 
5,890  volts.  If  everything  be  in  resonance,  the  spark  gap  can 
be  opened  to  %  inch,  when  3j/2  amperes  are  flowing.  As 
the  current  is  cut  down  by  cutting  in  resistance,  it  is  neces- 
sary to  cut  down  the  sparking  distance.  If  the  rheostat  is  cut 
out  and  555  turns  are  cut  in,  the  secondary  develops  7,624 
volts.  444  turns  gives  in  the  neighborhood  of  9,000  volts, 
333  turns  about  13,000  volts,  and  222  -turns  about  19,000  volts. 
100  turns  will  give  39,000  volts.  These  voltages  are  developed 
only  when  the  proper  amount  of  current  is  allowed  to  flow. 
The  water  rheostat  should  be  used  in  each  case  to  regulate 
the  flow. 


76  WIRELESS  TELEGRAPHY  AND 

The  spark  gap  practically  shorts  the  secondary,  and  if 
the  water  rheostat  is  not  used,  an  excessive  current  flows,  the 
voltage  drops  across  the  primary  and  the  transformer  is  heavily 
overloaded.  The  spark  gap  arcs  and  a  very  poor  result  is 
obtained. 

If  no  condenser  be  put  in  the  secondary,  a  regular  electric 
light  arc  can  be  drawn,  from  the  terminals  of  the  secondary. 
This  arc  is  of  no  use  in  the  production  of  wireless  signals  or 
high  frequency  manifestations,  as  its  frequency  is  only  50 
or  60  cycles  per  second.  If  too  little  condenser  be  used,  the 
spark  discharge  arcs  more  or  less  and  destroys  the  oscillations. 
Hence  enough  condenser  must  be  cut  in  to  prevent  this  arcing. 

With  555  turns  about  4  amperes  should  be  allowed  to 
flow;  444  turns,  5  amperes;  333  turns,  6.6  amperes;  and  222 
turns,  10.5  amperes. 

In  this  connection  it  must  be  remembered  that  this  is  a 
200-watt  transformer.  Now  a  200-watt  transformer,  if  prop- 
erly designed  and  used,  should  use  only  2  amperes.  With 
1,200  turns  in  the  primary,  this  would  give  2,400  ampere  turns. 
If  turns  are  cut  out,  more  current  must  be  allowed  to  flow 
to  get  the  same  number  of  ampere  turns. 

The  product  of  the  amperes  by  the  turns  in  each  case 
above  gives  approximately  2,400  ampere  turns.  If  no  rheo- 
stat be  used,  it  is  found  that  more  current  flows  in  each  case 
than  is  designated  above.  Hence  when  the  turns  are  cut  out, 
the  rheostat  must  be  used  to  regulate  the  current  to  the  right 
amount. 

Even  if  this  be  done,  the  iron  is  being  worked  at  higher 
and  higher  densities,  and  the  transformer  is  not  a  200-watt, 
but  much  higher.  If  10  amperes  are  allowed  to  flow,  the  iron 
is  being  worked  beyond  the  point  of  saturation,  and,  although 
10  amperes  are  flowing  in  the  primary,  the  iron  cannot  trans- 
form it,  and  the  transformer  is  being  worked  at  a  large  loss. 
Therefore,  as  the  turns  are  cut  out,  the  current  should  not  be 
allowed  to  rise  as  high  as  10  amperes. 

Furthermore,  the  No.  15  wire  of  the  primary  can  carry 
10  amperes  only  intermittently  and  for  a  very  short  time  with- 
out heating.  It  can  carry  5  or  6  amperes  intermittently  for 


HIGH  FREQUENCY  ELECTRICITY  77 

some  time  without  undue  heating,  and  in  this  transformer  at  all 
voltages  only  that  amount  should  be  allowed  to  flow  at  most. 

By  using  the  water  rheostat,  when  cutting  out  turns,  any 
of  the  above  voltages  can  be  used  and  as  much  current  allowed 
to  flow  as  will  work  the  best  in  each  case.  When  the  higher 
voltages  are  used,  the  spark  gap  can  be  opened  wider  and 
wider. 

In  the  operation  of  the  transformer  for  wireless  and  for 
high  frequency  experiments,  many  difficulties  will  be  encount- 
ered that  can  only  be  overcome  by  experience  and  practice. 

To  start  with,  just  enough  condenser  should  be  cut  in  to 
prevent  arcing  when  a  small  current  is  flowing.  Tune  by 
varying  the  turns  included  in  the  sending  helix  between  C 
and  Si,  Fig.  48,  until  the  best  result  is  obtained.  Now  vary 
the  current  and  the  spark  gap  until  the  result  is  improved. 

If  there  be  any  redness  in  the  aerial  spark  gap  or  in  the 
oscillation  spark  gap,  too  little  condenser  is  being  used  and 
more  should  be  added. 

Just  five  factors  are  concerned  in  this  operation,  viz. : 
1,  current;  2,  voltage;  3,  condenser;  4,  spark  gap;  5,  induct- 
ance. In  order  to  secure  the  best  result,  it  is  necessary  to 
adjust  these  five  factors  until  they  act  in  perfect  harmony. 

When  the  red  transformer  discharge  is  produced  in  either 
the  closed  oscillation  circuit  or  in  the  aerial  spark  gap,  no 
electro-magnetic  waves  are  set  up  in  the  ether  that  are  power- 
ful enough  for  the  purpose  of  wireless.  The  white  oscillatory 
discharge  of  the  condenser  is  necessary. 

These  factors  should  be  adjusted  until  the  aerial  spark  is 
fat  and  white.  The  aerial  spark  should  not  be  long,  but 
it  should  be  very  short,  white  and  fat.  Both  the  aerial  spark 
and  the  condenser  spark  should  have  a  good  tone  also.  It 
should  neither  be  ragged,  nor  hissing  in  tone. 

This  method  of  tuning  is  rough,  but  by  patient  work  one 
can  become  skilled  so  as  to  get  excellent  results.  Another 
method  will  be  given  later  in  the  chapters  on  theory. 

The  wave  length  sent  out  depends  upon  the  length  of  the 
aerial,  its  height  and  shape,  the  amount  of  wire  in  it,  and  the 
amount  of  turns  included  in  the  tuning  helix.  By  raising  or 


78  WIRELESS  TELEGRAPHY  AND 

lowering  the  point  D,  Fig.  48,  the  wave  length  is  changed. 
The  open  oscillation  circuit  has  a  natural  time  period  and 
fixed  wave  length.  The  closed  oscillation  circuit  Ci,  Si,  C 
must  be  tuned  to  this  by  varying  the  number  of  plates  in- 
cluded in  the  condenser  and  the  number  of  turns  included  in 
the  helix  between  the  points  Si  and  C.  If  too  much  current 
be  used,  more  condenser  must  be  used  and  the  closed  oscilla- 
tion circuit  is  thrown  out  of  tune  with  the'  open  oscillation 
circuit. 

When  the  closed  oscillation  circuit  is  tuned  to  the  open 
or  aerial  oscillation  circuit,  the  best  work  can  be  done. 

Even  in  this  case  two  wave  lengths  are  sent  out  by  the 
aerial  and  further  adjusting  should  be  done  to  get  these  two 
waves  as  near  together  as  possible. 

The  importance  of  regulating  the  current  is  very  great. 
As  has  been  said  before,  this  can  be  done  by  an  adjustable 
impedence,  a  water  resistance,  or  a  resistance  made  of  any 
of  the  resistance  wires,  such  as  german  silver  or  climax  wire. 

Do  not  be  discouraged  if  you  are  not  able  to  accomplish 
great  results  right  away.  Practice  works  wonders.  Be  pa- 
tient and  in  time  you  will  acquire  the  skill  of  manipulation  that 
is  necessary  to  success. 

Remember  that  big  transformers  on  little  aerials  can  ac- 
complish nothing  to  what  the  right  size  transformer  can  ac- 
complish. An  aerial  has  a  certain  capacity  and  it  can  be 
charged  to  hold  only  a  definite  amount  of  electricity.  When 
this  point  is  reached,  it  is  folly  to  try  to  pour  more  electricity 
into  it,  because  it  will  leak  out  into  the  air  in  every  direction 
and  also  be  wasted  as  heat  in  the  spark  gap.  The  energy 
is  not  only  wasted,  but  it  acts  as  a  detriment  as  well.  The 
right  amount  of  current  is  necessary  to  perfect  tuning  and 
tuning  accomplishes  results.  It  is  surprising  what  can  be 
done  on  small  current  with  small  transformers  and  proper 
tuning. 

As  time  passes  and  skill  is  acquired,  you  will  be  able  to 
accomplish  more  and  more  with  the  same  apparatus. 

Care  should  be  taken  not  to  interfere  with  the  commercial 
companies  in  their  work.  In  order  not  to  do  this,  it  is  neces- 


HIGH  FREQUENCY  ELECTRICITY 


79 


sary  to  have  a  delicate  detector  so  as  to  know  when  far-away 
stations  are  working  with  them.  With  the  detectors  and 
telephones  described  here,  there  need  not  be  much  danger  of 
annoying  them.  Always  listen  first  before  sending,  in  order 
to  know  whether  the  way  is  clear. 

When  high  frequency  apparatus  is  to  be  operated,  it  is 
put  in  the  place  of  the  tuning  helix  of  the  aerial  and  adjust- 
ments and  tuning  is  proceeded  with  in  the  same  way. 

Tune  until  the  longest  sparks  can  be  obtained  from  the 
apparatus. 


Fig.  49.     Inductively   connected   sending   circuit. 

M,  transformer;  N,  alternator;  C,  condenser;  D,  spark  gap;  T,  air 
core  transformer;  A,  aerial. 


The  tuning  circuits  used  here  are  known  as  the  direct 
connected  or  loosely  coupled  method.  Close  coupling  and  in- 
ductive connections  can  be  used  instead,  if  desired,  but  it 
requires  more  skill  to  obtain  results.  Fig.  49  gives  the  in- 
ductive method.  N  is  the  source  of  electrical  energy,  M  is  the 
transformer,  C  is  an  adjustable  condenser,  D  is  a  spark  gap 
and  T  is  a  Tesla  coil,  having  four  turns  in  the  primary  and 
from  twenty  to  forty  in  the  secondary.  The  primary  and 
secondary  are  close  together  and  imbedded  in  wax  or  oil. 

This  construction  of  the  Tesla  coil  will  be  described  later. 
The  inductive  method  both  in  sending  and  receiving  is  used 
where  selective  tuning  is  necessary.  Selective  tuning  is  dif- 
ficult and  should  not  be  attempted  by  the  amateur  until  he 
has  mastered  the  other  method.  The  .ratio  and  number  of 


80 


WIRELESS  TELEGRAPHY  AND 


turns  must  be  accurately  adjusted  to  the  aerial  used  and  tuning 
is  accomplished  by  adjusting  the  condenser. 


Fig.  50.     Simplest  form  of  receiving  device. 
A,  aerial;   D,  detector;   G,  ground;   E,  battery;   T,  telephone. 

2.  The  Receiving  Circuits. — The  simplest  kind  of  a  re- 
ceiving circuit  is  shown  in  Fig.  50.  D  is  the  detector  to  which 
the  aerial  is  directly  joined.  The  ground  G  is  attached  to  the 
other  side  of  the  detector.  A  telephone  T  with  or  without 
the  battery  E  is  shunted  around  the  detector  as  shown  in  the 
cut.  Without  the  battery  and  by  the  use  of  the  iron  pyrite 
detector,  this  works  excellently  for  short  distances. 

No  tuning  can  be  done,  however,  and  noises,  due  to  in- 
duction, are  very  strong,  owing  to  electric  light  circuits  and 


o  \ 


OOOOOOV- 


Fig.  51.     Receiving  circuit  with  tuning  coil  added. 


HIGH  FREQUENCY  ELECTRICITY 


81 


car  line  circuits.  The  noises  in  the  telephone  are  very  annoying 
and  long  distance  work  is  impossible.  If  a  battery  be  used,  a 
potentiometer  should  be  used  in  series  with  it  and  the  tele- 
phone in  order  to  regulate  the  voltage  across  the  detector. 

With  the  silicon  and  iron  sulphide  detector,  however,  no 
battery  is  necessary.  In  fact,  unless  one  has  a  potentiometer 
containing  a  high  resistance,  the  battery  is  a  detriment. 

A  great  improvement  is  secured  by  adding  a  tuning  coil 
as  shown  in  Fig.  51.  By  this  means  the  induction  or  humming 
in  the  telephone  is  partly  cut  out  and  tuning  is  made  possible. 


Fig.  52.     Receiving  circuit,  with  tuning  coil  I  and  condenser  C  added, 
forming  closed  oscillation  circuit  MCDNI,  non-inductively  connected. 

Longer  distances  can  be  worked  over  and  near-by  sta- 
tions come  in  louder. 

A  still  greater  improvement  is  secured  by  including  a  con- 
denser in  the  circuit,  as  shown  in.  Fig.  52,  thus  forming  a 
closed  oscillating  circuit.  In  this  figure,  A  is  the  aerial  which 
should  be  attached  to  a  sliding  contact.  /  is  the  tuning  coil 
described  in  Figs.  39  and  40.  G  is  the  ground.  D  is  the  de- 
tector with  a  sliding  contact  at  N.  C  is  the  condenser  de- 
scribed in  Figs.  41  and  42.  Its  connection  to  the  tuning  coil 
at  M  may  be  sliding  or  fixed.  T  is  the  telephone  shunted 
around  the  detector. 


82 


WIRELESS  TELEGRAPHY  AND 


The  detector  D,  the  tuning  coil  7  and  the  condenser  C 
form  a  closed  oscillation  circuit  in  which  close  tuning  can  be 
accomplished.  All  low  frequency  waves  due  to  electric  lights, 
motors  and  street  cars  fail  to  set  up  oscillations  in  the  closed 
circuit,  because  their  time  periods  are  not  the  same  as  that 
of  the  closed  circuit.  When  waves  having  the  same  per- 
iods of  frequency  of  oscillation  arrive,  they  set  up  oscillations 
in  the  closed  circuit,  when  that  is  adjusted  by  changing  the  in- 
ductance and  capacity  so  as  to  secure  resonance.  All  this 
will  be  explained  later. 


A 


ri 


n 


D 
T-T 


N 


wwwv 


Fig.  53.     Receiving  circuit,  with  potentiometer,  P,  added. 

A,  aerail;  M,  condenser  sliding  contact;  N,  detector  sliding  con- 
tact; G,  ground;  S,  sliding  contact  on  potentiometer  P;  T,  telephone, 
non-inductively  connected. 

Wherever  battery  is  used,  a  potentiometer  should  be  used. 
Fig.  5J  gives  the  connections  for  the  potentiometer  and  the 
telephone  T  described  in  Figs.  45  and  46,  except  that  N  and 
A  are  connected  to  the  same  slide.  The  battery  is  shorted 
through  the  resistance  S.  One  terminal  of  the  telephone  is 
attached  to  the  condenser  and  detector.  The  other  terminal 


HIGH  FREQUENCY  ELECTRICITY 


83 


of  the  telephone  is  attached  to  the  sliding  contact  of  the  po- 
tentiometer. 

The  resistance,  battery  and  telephones  can  be  put  in  series 
if  desired.  With  the  electrolytic  detector  the  potentiometer 
is  a  necessity.  It  is  useful  with  carborundum,  but  with  iron 
pyrite  and  silicon  it  is  absolutely  unnecessary. 


Fig.  54.     Inductively  connected  receiving  set. 
T,   Tesla   coil   or   air   core   transformer. 


This  receiving  set  is  a  direct  connected  or  loosely  coupled 
one.  For  selective  tuning  the  inductive  connection  shown  in 
Fig.  5^"is  necessary.  T  is  a  Tesla  coil  having  twice  as  many 
turns  on  the  primary  as  on  the  secondary.  They  are  wound 
one  over  the  other.  They  must  be  made  to  harmonize  with 
the  aerial  with  which  they  are  to  be  used. 

The  circuits  shown  here  are  fundamental.  No  attempt 
will  be  made  in  this  book  to  present  the  modifications  and 
their  names.  One  or  two  modifications  will  be  given  further 
on,  in  connection  with  the  theory  of  the  subject. 

With  the  circuit  shown  in  Fig.  53  and  with  the  apparatus 
described,  the  boys  of  Los  Angeles  have  been  able  to  do  some 
pretty  keen  work. 

The  condenser  and  inductance  can  be  made  very  care- 
lessly. In  fact,  if  the  inductance  be  made  by  winding  some 
No.  24  cotton  covered  wire  on  a  cylinder  of  wood  and  the  in- 
sulation be  scraped  off  to  allow  the  contact  point  to  rest  on 
the  metal,  and  if  the  condenser  be  made  up  of  a  few  sheets 


84  WIRELESS  TELEGRAPHY  AND 

of  tin  foil  and  paraffined  paper,  everything  will  work  all  right 
provided  one  has  the  right  detector  and  telephones. 

The  detector  is  the  most  important  piece  of  apparatus  of 
the  whole  receiving  outfit.  One  may  have  the  finest  apparatus 
in  the  world,  but  if  the  detector  is  not  sensitive,  one  cannot 
work  over  anything  but  very  short  distances.  One  may  have 
the  worst  looking  apparatus  in  the  world,  but  if  the  detector  is 
all  right,  one  can  work  over  long  distances  with  ease. 

3.  The  Telephone. — Next  to  the  detector,  the  telephone 
is  a  most  important  piece  of  apparatus.  It  is  not  an  easy 
matter  to  get  a  good  telephone.  Their  sensitiveness  is  usually 
quoted  in  ohms,  but  it  must  be  remembered  that  the  resistance 
is  a  detriment  to  a  telephone  rather  than  a  help. 

It  is  not  the  resistance  that  makes  the  telephone  sensitive, 
but  the  number  of  turns  of  wire  around  the  magnets.  It  is 
the  number  of  ampere  turns  around  the  poles  of  the  permanent 
magnets  of  the  telephones  that  does  the  work.  One  turn  of 
wire  carrying  one  ampere  is  an  ampere  turn.  One  turn  of  wire 
carrying  two  amperes  is  two  ampere  turns.  Ten  turns  of  wire 
carrying  one-tenth  of  an  ampere  is  one  ampere  turn. 

Since  the  telephone-  has  to  do  with  very  weak  currents, 
a  great  many  turns,  the  more  the  better,  must  be  put  around 
the  poles  in  order  that  the  weak  current  may  set  up  the  lines 
of  force  necessary  to  influence  the  diaphragm  of  the  telephone. 
As  the  number  of  turns  increases,  the  resistance  increases,  and 
this  resistance  weakens  the  current. 

To  begin  with,  the  ampere  turns  increase  in  their  effect 
faster  than  the  effect  due  to  increase  in  resistance.  But  as  the 
turns  are  laid  on,  the  wire  in  one  turn  becomes  longer  and 
hence  each  turn  has  more  resistance.  Finally  a  time  is  reached 
where  the  effect  due  to  resistance  is  greater  than  the  effect 
due  to  the  ampere  turns,  and  it  does  no  good  to  go  on  adding 
turns.  Furthermore,  as  the  turns  are  put  on  they  are  further 
away  from  the  core  of  the  pole,  and  for  this  reason  their  effect 
is  less  for  each  turn.  Thus  it  is  seen  that  as  the  turns  are 
put  on,  the  resistance  begins  to  rapidly  increase  and  the  effect 
of  the  ampere  turns  to  decrease. 


HIGH  FREQUENCY  ELECTRICITY  85 

Because  a  receiver  is  a  2,000-ohm  receiver  and  costs  from 
$7.00  to  $12.00,  is  no  sign  that  it  is  a  good  receiver  for  wireless. 

The  thinness  of  the  diaphragm  and  the  air  gap  between  it 
and  the  poles  of  the  magnets  are  also  factors  in  its  sensi- 
tiveness. 

For  long  distance  work  the  diaphragm  should  be  very 
close  to  the  poles  of  the  magnets,  but  not  near  enough  to  reach 
them  in  its  vibration. 

The  thinner  the  diaphragm  the  greater  the  magnetic  re- 
luctance, but  this  is  offset  by  its  greater  sensitiveness  due  to  its 
thinness.  If  the  permanent  magnets  are  too  strong,  the  iron 
of  the  diaphragm  becomes  saturated  and  the  telephone  be- 
comes less  sensitive. 

It  is  commonly  supposed  that  the  telephone  will  not  re- 
spond to  high  frequency  alternating  currents,  but  this  is  a 
mistaken  idea.  If  the  connections  be  made  for  sending  as 
shown  in  Fig.  75,  the  telephones  can  be  disconnected  from  the 
apparatus  entirely,  and  when  one  is  near  the  aerial  with  them, 
they  respond  loudly  and  clearly.  If  one  terminal  of  the  tele- 
phone is  taken  in  the  hand  and  the  other  is  allowed  to  hang 
freely,  the  effect  is  greatly  increased. 

The  telephone  thus  becomes  a  detector  to  very  high  fre- 
quency waves  in  the  ether.  If  the  telephone  is  shunted  around 
the  condenser,  it  works  about  as  well  as  when  it  is  shunted 
around  the  detector. 

If  the  ordinary  connections  are  made,  as  is  usual  when 
sending,  and  the  above  experiments  are  tried,  the  telephones 
will  be  silent.  In  the  latter  case  the  frequency  is  much  lower. 

Pulsating  lines  of  force  are  probably  set  up  in  the  tele- 
phone and  these  act  independently  of  the  molecules  of  the  iron, 
but  set  up  eddy  currents  in  the  diaphragm.  The  reaction  be- 
tween the  field  set  up  by  these  eddy  currents,  and  the  field  of 
the  permanent  magnets  must  be  responsible  for  these  results. 

The  strength  of  the  magnets  is  another  factor  in  making 
a  good  telephone.  It  is  very  difficult  to  make  magnets  that 
will  stay  permanent.  A  great  many  of  the  magnets  in  the 
telephones  lose  their  strength  quickly  and  then  they  are 
useless. 


86  WIRELESS  TELEGRAPHY  AND 

The  telephones  are  quoted  in  terms  of  their  resistance,  be- 
cause that  is  the  easiest  way  to  quote  them. 

I  have  a  75-ohm  receiver  on  my  desk  that  is  better  than 
any  2,000-ohm  receiver,  with  one  exception,  that  I  have  yet 
examined.  It  is  one  of  the  Bell  telephones  that  is  used  in 
a  house  telephone  set,  but  it  is  very  sensitive.  I  have  pitted 
several  navy  telephones  against  it,  but  for  long  distance  it  is 
better  than  any  of  them.  However,  I  tried,  a  few  days  ago, 
one  of  the  Collins  wireless  telephones  and  found  it  to  be 
excellent.  It  was  very  much  better  than  my  75-ohm  receiver. 
The  magnets  were  strong  and  the  telephones  were  very  sensi- 
tive on  long  distances. 

4.  To  Operate  the  Receiving  Instruments. — First  adjust 
the  detector  until  the  static  is  plainly  heard.  By  static  is  meant 
the  crackling  that  one  hears  in  the  telephones  when  everything 
is  in  good  adjustment.  This  static  is  due  to  a  great  many  dif- 
ferent things.  The  sparking  of  the  trolley  upon  the  street 
cars,  and  the  effects  due  to  atmospheric  conditions,  cause  .it. 
Lightning  discharges  far  or  near  cause  it,  as  well  as  electro- 
magnetic waves  from  the  sun. 

A  sensitive  point  is  found  by  moving  the  crystal  about 
until  this  result  is  obtained.  All  points  are  not  equally  sensi- 
tive. Some  parts  of  the  crystal  will  be  found  to  be  dead 
entirely. 

Having  found  such  a  point,  slide  the  contacts  on  the 
tuning  inductance  back  and  forth  until  something  is  heard. 
If  some  one  is  working,  you  may  get  them  faintly.  Then  ad- 
just the  sliding  contacts  until  the  signals  are  at  a  maximum. 
Set  the  condenser  on  different  contacts  and  readjust  the  in- 
ductance, until  the  right  amount  of  condenser  is  found  for  any 
particular  station.  It  will  be  found  that  a  small  condenser 
is  better  for  long  distance,  while  a  large  condenser  will  bring 
in  near-by  stations  the  louder. 

If  a  potentiometer  and  battery  are  being  used,  the  resist- 
ance of  the  potentiometer  must  also  be  adjusted  for  the  best 
result. 

If  too  much  condenser  is  used,  the  sounds  become  mushy 


HIGH  FREQUENCY  ELECTRICITY  87 

and  finally  weak.  The  right,  amount  of  condenser  renders  the 
sounds  in  the  telephone  sharp  and  clear. 

The  coherer  is  not  described  in  this  book.  It  is  not  as 
sensitive  as  the  detectors  here  described.  If  any  mechanical 
work  is  done,  however,  such  as  ringing  bells,  etc.,  the  coherer 
is  necessary.  It  is  described  in  other  books. 

5.  Working  Distance  of  a  Station. — The  working  dis- 
tance of  a  station  depends  upon  several  factors :  The  height 
of  the  aerial,  the  amount  of  wire  in  it,  their  distance  apart,  the 
amount  of  the  aerial  that  is  horizontal,  its  location,  and  last, 
but  not  least,  the  skill  of  the  operator. 

The  greater  the  capacity  the  aerial  has,  the  more  energy 
it  can  handle  and  the  more  powerful  the  waves  that  it  can 
send  out.  Height  is  only  one  factor.  Although  height  above 
the  ground  decreases  the  capacity  of  a  suspended  wire  with 
reference  to  the  ground,  it  actually  increases  the  capacity 
for  a  vertical  aerial  because  it  adds  more  wire  to  it. 

The  great  mistake  is  usually  made  of  using  more  current 
in  the  closed  oscillating  circuit  than  the  capacity  of  the  aerial 
warrants.  The  aerial  has  a  fixed  oscillation  constant,  due  to 
its  capacity  and  inductance.  These  factors  cannot  be  varied 
very  much,  and  if  a  large  current  is  used  in  the  primary  of 
the  transformer,  more  condenser  must  be  used  in  the  closed 
oscillation  circuit  in  order  to  handle  the  additional  current. 
This  throws  the  closed  oscillation  circuit  completely  out  of 
tune  with  the  open  radiating  circuit  and  consequently  good 
work  cannot  be  done.  Less  current  and  better  tuning  would 
reach  much  farther. 

In  order  to  have  a  long  distance  station,  then,  it  is  neces- 
sary to  increase  the  size  of  the  aerial.  This  can  be  done  by 
making  it  higher  or  by  increasing  the  number  of  wires  in  it. 

The  addition  of  more  powerful  transformers  will  accom- 
plish nothing,  provided  the  aerial  is  already  working  up  to  its 
full  capacity. 

An  aerial  must  be  very  large  to  require  a  kilowatt  trans- 
former to  properly  operate  it.  The  aerials  usually  put  up  by 
the  boys  will  operate  best  upon  a  200  to  a  300-watt  trans- 
former. In  this  case  the  iron  used  in  the  core  must  be  of  the 
best. 


WIRELESS  TELEGRAPHY  AND    < 


Plate  IV.     Photograph  of  Tesla  coil  or  air  core  transformer,  built  at 
the  Los  Angeles  Polytechnic  High  School.     36-inch  maximum  spark. 


HIGH  FREQUENCY  ELECTRICITY  89 

CHAPTER  VI. 

HIGH   FREQUENCY   APPARATUS. 

1.  The  Tesla  Coil. — The  phenomena  that  can  be  pro- 
duced with  high  frequency  apparatus  is  very  beautiful,  inter- 
esting "and  instructive. 

With  a  200-watt  transformer,  condenser  and  spark  gap 
described  in  this  book,  and  the  following  apparatus,  X-ray 
tubes,  Crooke's  tubes  and  Geisler  tubes  can  be  run.  For  these 
experiments  Tesla  coils  or  Oudin  resonators  are  necessary. 
They  can  be  made  in  all  sizes.  The  smaller  ones  do  not  cost 
very  much. 

The  lengths  of  these  coils  should  be  about  three  and  a 
half  times  their  diameter,  and  the  primary  should  be  about 
twice  the  diameter  of  the  secondary. 

The  design  given  here  is  for  a  large  size,  suitable  for  a 
kilowatt  transformer,  developing  10,000  or  20,000  volts  on  the 
high  side.  Smaller  ones  should  be  made  for  the  200-watt 
transformers. 

Cut  out  of  inch  wood  four  annular  blocks,  A  and  B,  Fig. 
55,  2  feet  in  diameter,  making  the  rings  2  inches  wide.  Dowel 
and  glue  them  together  in  pairs,  crossing  the  grain  of  the 
wood  so  as  to  form  the  two  blocks  A  and  B.  The  rings  can 
be  cut  in  parts  of  arcs  of  circles  and  then  assembled,  glued  and 
doweled  together.  See  photograph  of  complete  coil,  Plate  IV. 

Divide  the  circumference  of  the  rings  into  16  or  18  parts 
and  bore  ><-inch  holes  D  in  the  rings.  Obtain  as  many  pieces 
of  wood  E,  1  inch  square  and  9  inches  long.  Turn  down 
each  end  a  distance  of  y2  inch  to  fit  the  ^-inch  holes  in  the 
rings  A  and  B.  Fit  these  into  the  holes  so  as  to  form  the 
cage  ABFD. 

Cut  out  of  inch  stuff  a  couple  of  circular  blocks  //,  20^ 
inches  in  diameter.  Glue  and  dowel  them  together,  crossing 
the  grain  so  as  to  form  the  center  piece  H.  In  the  center  of 
this  block  make  a  square  hole  2  inches  by  2  inches. 

Out   of   inch   stuff   cut    12   circular   blocks   /   and   G,   and 


90 


WIRELESS  TELEGRAPHY  AND 


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bfl 

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HIGH  FREQUENCY  ELECTRICITY  91 

in  their  centers  cut  holes  2  inches  square.  Fit  one  of  these 
on  each  side  of  the  block  H,  gluing  and  doweling  them  to- 
gether. 

Obtain  a  piece  of  wood  '0,  2  inches  square  and  51  inches 
long.  Put  the  combination  block  PIG  upon  the  center  of  this 
piece  0,  and  fix  it  firmly  in  position.  Arrange  the  other  blocks 
five  on  each  side,  equidistance  along  0,  as  shown  at  /  in  the 
cut,  placing  two  of  them  at  the  extreme  ends  of  O. 

Over  the  blocks  /,  on  each  side  of  //,  wrap  leatheroid, 
an  insulating  paper.  Wrap  this  around  three  or  four  times 
in  order  to  form  a  stiff  drum.  On  the  drum  thus  formed, 
wind  850  to  1,000  turns  of  No.  24  single  cotton  covered  magnet 
wire.  Do  not  let  the  wires  touch.  They  can  be  spaced  in  the 
following  manner: 

Put  the  drum  in  the  lathe  or  suspend  it  otherwise,  so  that 
it  can  be  rotated.  Make  a  loop  of  copper  wire,  having  a  di- 
ameter equal  to  the  spacing  desired.  Attach  a  weight  to  the 
loop  and  put  it  over  the  drum,  allowing  the  weight  to  hang 
below.  The  loop  should  be  long  enough  to  allow  the  weight 
to  hang  about  2  feet  below  the  drum.  Start  on  the  left  to 
wind,  turning  the  drum  away  from  you.  After  putting  on  the 
first  turn,  place  the  guide  wire  by  the  side  of  the  turn  just 
wound.  As  you  wind,  the  guide  wire  will  move  along  and 
attend  to  the  spacing,  the  guide  wire  being  between  the  turn 
just  wound  and  the  turn  just  going  on. 

When  the  middle  of  the  block  H  is  reached,  bore  a  hole 
in  it.  Break  the  wire  and  carry  the  end  through.  Splice  the 
broken  ends  and  go  on  with  the  winding.  Put  screws  into  the 
end  blocks  and  solder  the  wire  to  the  screws.  Assemble  the 
pieces  E,  and  one  side  of  the  cage,  using  glue.  Place  the 
cage  thus  half  assembled  over  the  drum,  fitting  the  middle 
of  the  pieces  E  on  to  the  piece  H.  Put  glue  on  the  ends  of 
E  and  put  on  the  end  AD.  Drill  holes  in  the  middle  of  each 
piece  E  and  into  H.  Drive  pegs  into  these  holes,  in  order  to 
hold  the  cage  ABED  firmly  in  place  on  H. 

Prepare  two  supports  /,  18  inches  high  and  1  inch  thick, 
and  four  braces  K,  12  inches  long  and  12  inches  high.  The 
support  /  should  be  rounded  out  to  fit  the  cage. 


92 


WIRELESS  TELEGRAPHY  AND 


Plate  V.     Photograph  of  Tesla  coil,  shown  in  Plate  IV,  giving  a  24- 
inch  discharge.     Exposed  10  seconds.     Made  by  Mr.  Parke  Hyde, 
a  pupil  of  the  Los  Angeles  Polytechnic  High  School. 


HIGH  FREQUENCY  ELECTRICITY  93 

Support  the  whole  upon  the  base  L,  52  inches  long  and 
30  inches  wide.  Take  two  pieces  N,  2  inches  by  2  inches  and 
30  inches  long.  Cut  from  fiber  or  wood  two  circular  end 
pieces,  not  shown  in  the  cut,  a  little  larger  in  diameter  than  the 
drum.  Cut  a  hole  in  them  large  enough  to  admit  the  end  of  the 
piece  0.  Put  them  over  0  and  screw  them  to  the  end  piece 
already  there.  Saw  off  0  flush  with  this  end  piece  and  put 
TV  in  place  solidly  against  this  end  piece,  screwing  it  to  0  and 
the  end  piece.  Take  two  'pieces  of  brass  P,  2  inches  square 
and  y%  inch  thick.  Obtain  two  brass  tubes  2  inches  long  and 
y2  inch  in  diameter.  Melt  some  solder  and  fill  the  tubes  with 
it.  Through  the  solder  bore  holes  ^  inch  in  diameter.  Thread 
a  binding  post  T  in  the  tube.  Solder  the  brass  tube  Q  to  the 
brass  piece  P.  Screw  these  on  top  of  the  posts  N. 

Obtain  two  aluminum  rods,  ^  inch  in  diameter  and  fix 
2^-inch  rubber  handles  upon  them.  Put  the  aluminum  rods 
through  the  tube  Q.  Run  wires  from  the  terminals  of  the 
secondary  to  the  brass  pieces  P  and  solder  it  to  them. 

Obtain  about  60  feet  of  No.  5  spring  brass  wire  and  put 
around  the  cage  ABDF,  putting  the  turns  about  ^4  inch  apart, 
thus  having  10  turns  on  the  primary. 

2.  The  Oudin  Resonator. — The  drum  for  the  Oudin 
resonator  is  made  like  that  for  the  Tesla  coil,  with  the  excep- 
tion that  the  middle  piece  H  is  left  off  and  the  leatheroid  is 
wound  continuously  from  end  to  end.  0,  Fig.  56,  is  the  drum, 
11  inches  in  diameter  and  36  inches  high.  -On  this  is  wound 
from  800  to  1,000  turns  of  No.  26  D.C.C.  wire.  The  primary 
cage  is  made  the  same  as  in  the  other  case.  The  two  are 
assembled  upon  the  base  B,  which  rests  upon  rubber  legs  /. 
The  cage  A  and  the  drum  0  are  screwed  to  the  base  after 
being  centered. 

F  is  a  brass  rod  driven  into  a  hole  in  the  center  post,  and 
K  is  a  brass  ball  surmounting  this  rod.  M  is  an  upright 
post  having  dimensions  shown  in  the  cut,  and  C  is  a  binding 
post  for  the  ground  wire.  The  basket  A  is  made  the  same 
as  for  the  Tesla  coil.  Connect  the  bottom  of  the  primary  to 
the  bottom  of  the  secondary. 


94 


WIRELESS  TELEGRAPHY  AND 


Plate   VI.      Photograph   of   Oiulin   resonator,  24-inch    spark,   made   by 
Mr.  Parke  Hyde,  a  pupil  of  the  Los  Angeles  Polytechnic  High  School. 


HIGH  FREQUENCY  ELECTRICITY 


95 


vo 


0 


if 


A 


.B 


rubber 


Fig.  56.     Drawing  of  Oudin  resonator  shown  in  Plate  VI. 

3.  Operation. — In  order  to  operate  the  Tesla  coil  or  the 
Oudin  resonator  here  described,  a  kilowatt  transformer  is 
necessary. 

Either  20,000  or  10,000  volts  can  be  used,  but  we  have 
found  that  10,000  volts  give  us  the  maximum  results.  The 
condenser  for  operating  these  coils  must  be  larger  than  the 
one  described  in  Fig.  12.  Obtain  12  plates  of  window  glass 
18  inches  by  24  inches.  Leave  a  margin  of  at  least  2  inches  on 


96 


WIRELESS  TELEGRAPHY  AND 


three  sides,  and,  on  the  third  side,  where  the  contacts  are  to 
come  out,  leave  a  margin  of  4  inches.  Follow  the  general 
plan  given  in  Fig.  75.  A  helix  of  spring  brass  wire  can  take 
the  place  of  the  brass  rods  F  if  desired.  Then  the  contacts  can 
be  made  by  merely  slipping  the  contact  rods  in  between  the 
turns  of  the  helix  of  brass.  On  the  right  of  Plate  IV  this  con- 
denser can  be  seen. 


o 
o 

IT 

k^> 


Fig.   57.     Diagram   of  connections   of  Tesla   coil   shown   in   Plate    IV. 

To  operate  the  Tesla  coil  the  connections  should  be  made 
as  shown  in  Fig.  57.  .  The  source  of  alternating  current  A  is 
connected  in  series  with  the  water  rheostat  R,  and  the  primary 
of  the  transformer  T  and  a  switch  K.  The  terminals  of  the 
secondary  are  connected  to  tlie  condenser  C  as  shown.  From 
the  same  terminals  of  the  condenser,  wires  are  conducted  to 
the  primary  of  the  Tesla  coil  P.-  Tuning  is  effected  by  moving 
the  contacts  0  and  M  from  turn  to  turn,  and  by  adjusting  the 
plates  in  the  condenser.  G  is  the  spark  gap. 

With  a  kilowatt  transformer,  pulling  a  load  of  20  am- 
peres in  the  primary,  we  have  obtained  a  36-inch  spark  with 
the  Tesla  coil,  shown  in  Plate  IV.  This  overloads  the  trans- 
former, but  does  no  harm  for  short  intervals  of  time. 

To  operate  coils  of  this  size  requires  from  15  to  25  am- 
peres, and  a  2-kilowatt  transformer  would  be  much  better ; 
however,  they  work  very  well  with  a  kilowatt  size,  provided 
it  is  overloaded  in  order  to  get  the  proper  amount  of  energy. 

The  water  rheostat,  the  condenser,  the  primary  induct- 
ance of  the  Tesla  coil,  and  the  spark  gap  should  be  regulated 
until  the  maximum  result 'is  reached.  It  works  best  on  20,000 
volts. 


HIGH  FREQUENCY  ELECTRICITY 


97 


When  resonance  is   obtained,  the  ends  of  the  coil  send 

out   a   beautiful   spray   and   a   36-inch  spark   passes   between 

the  terminals  of  the  coil.     The  spark  points  should  be  filed 

clean  and  smooth  and  they  should  be  kept  that  way. 


(XM5000 

iXXXXXXX) 


Fig.  58.     Diagram  of  connections  for   Oudin   resonator  shown  in 

Plate  VI. 

The  connections  for  the  Oudin  resonator  are  given  in 
Fig.  $8.  The  connections  are  similar  to  those  given  in  Fig.  57, 
except  that  the  bottom  turn  of  the  secondary  is  connected  to 
the  bottom  turn  of  the  primary.  The  inductance  is  varied  by 
attaching  the  point  0  to  the  top  of  the  primary  turns,  and 
then  by  moving  M  up  or  down,  until  resonance  is  obtained, 
the  water  rheostat,  the  condenser  and  the  spark  gap  being 
adjusted  at  the  same  time.  This  resonator  works  the  best  on 
10,000  volts.  It  will  do  well  on  20,000,  however,  but  10,000 
gives  the  longest  streamers. 


98 


WIRELESS  TELEGRAPHY  AND 


Plate  VII.     Taking  a  16-inch  discharge  into  the  body  from  the  Oudin 
resonator.     Exposed  10  seconds. 


HIGH  FREQUENCY  ELECTRICITY  99 

We  have  obtained  streamers  2  feet  long  from  the  brass 
ball  and  have  been  able  to  take  them  through  the  body  with- 
out harm. 

To  do  this  a  person  should  stand  on  an  insulating  stand 
made  of  wood,  supported  on  glass  legs.  See  Plate  VII.  Take 
a  metal  rod  in  the  hand  and  approach  it  to  the  terminal  K, 
Fig.  56.  The  spark  will  pass  to  the  rod  and  the  current  will 
oscillate  into  and  out  of  the  body.  If  everything  is  in  reson- 
ance and  the  spark  gap  is  not  too  wide  open,  one  does  not  feel 
the  discharge  at  all. 

If  the  spark  gap  is  wide  open,  the  current  causes  the 
muscles  of  the  arm  to  contract  somewhat,  but  not  disagree- 
ably. In  doing  this  a  person  should  not  make  a  good  ground, 
as  the  shock  then  becomes  very  disagreeable.  In  all  our  ex- 
perience with  a  kilowatt  transformer  and  this  apparatus,  no 
one  has  received  the  slightest  injury. 

On  one  occasion,  while  the  coil  was  running  full  blast,  one 
of  our  students  fell  upon  the  top  of  the  condenser  and  received 
no  injury,  although  it  scared  him  somewhat.  These  high 
frequency  oscillations  are  not  dangerous  and  the  reasons  for 
it  will  be  given  under  the  head  of  the  theory. 

Geisler  or  vacuum  tubes  held  in  the  hand  anywhere  near 
these  coils  light  up  brightly,  without  any  contact  with  the 
apparatus. 

The  two  instruments  just  described  are  not  fit  for  wire- 
less. Although  they  send  out  waves,  there  are  too  many  turns 
in  the  secondaries  and  they  do  not  work  as  well  as  the  simple 
tuning  helix  described  in  Fig.  21. 

Small  coils  can  be  made  for  the  200  or  300-watt  outfits  by 
merely  varying  the  size,  making  the  length  3*/2  times  the  di- 
ameter and  the  primary  twice  the  diameter  to  the  secondary. 

An  Oudin  resonator  that  will  light  a  lamp  through  the 
body  and  work  well  on  300-watt  transformer,  is  made  as  fol- 
lows :  Make  a  drum  10  inches  long  and  3^  inches  in  diameter. 
Put  on  about  300  turns  of  No.  34  D.C.C.  wire.  Make  a  pri- 
mary cage  7  inches  in  diameter  and  3^2  inches  high.  Put 
10  turns  of  No.  10  bare  copper  wire  on  this,  and  connect  the 


100 


WIRELESS  TELEGRAPHY  AND 


Plate  VIII.     Photograph  of  lighting  the  lamp  through  the  body  from 

a  small  Oudin  resonator.     220-volt,  110  16-candle-power  lamp 

brought    to   full    candle    power. 


HIGH  FREQUENCY  ELECTRICITY  101 

bottom  of  the  secondary  to  the  bottom  of  the  primary.  The 
copper  turns  should  be  spaced  evenly,  In  order  to  light  the 
lamp,  connect  as  in  Fig.  58. 

Tune  until  a  good  hot  spark  is  obtained,  by  approaching 
a  rod  held  in  the  hand  near  the  terminal  of  the  Oudin.  Take 
an  ordinary  110- volt  16-candle-power  electric  light  and  solder 
copper  wire  to  .the  outside  and  inside  contacts.  Solder  on  to 
the  ends  of  these  wires  brass  pieces  about  4  inches  long  and 
2  inches  wide  for  the  purpose  of  handles.  Brass  tubes,  how- 
ever, make  good  handles.  Put  one  terminal  wire  of  the  lamp 
on  the  terminal  of  the  Oudin  and  take  the  other  terminal  in 
the  hand.  Stand  on  the  insulating  stool  and  turn  on  the  cur- 
rent. The  current  surges  into  the  body  and  back  again 
through  the  lamp,  lighting  it  to  full  candle  power  if  everything 
is  in  resonance. 

A  better  piece  of  apparatus  for  this  purpose  is  made  as 
follows:  Take  an  ordinary  quart  beer  bottle.  A  two-quart 
bottle  is  better  if  it  can  be  obtained.  Wind  No.  34  wire  on 
the  bottle,  beginning  at  the  bottom  and  finishing  at  the  shoul- 
der of  the  bottle.  Bring  the  top  terminal  up  to  a  brass  rod 
fixed  in  a  cork  in  the  bottle.  Imbed  this  in  an  inch  of  wax. 
Take  Xo.  12  rubber  covered  wire  and  put  five  turns  of  it 
around  the  bottom  of  the  bottle,  winding  the  turns  as  closely 
together  as  possible,  and  as  near  the  bottom  as  possible.  Con- 
nect as  shown  in  Fig.  58.  Vary  the  plates  until  the  best  re- 
sults are  obtained.  Take  off  a  turn  or  put  on  a  turn  and  by 
trial  determine  the  number  of  turns  that  accomplish  the  best 
result.  After  this  is  done,  imbed  the  whole  thing  in  a  prepara- 
tion of  wax,  to  a  depth  of  a  couple  of  inches. 

This  insulation  is  necessary  to  obtain,  the  best  result,  as 
there  is  heavy  leakage  between  turns  without  it.  There  is  a 
tendency  to  break  down  between  the  primary  and  the  second- 
ary, but  it  can  be  easily  repaired.  If  it  be  worked  on  10,000 
volts,  it  works  better  than  on  higher  voltages  and  it  does  not 
then  break  down.  Tune  as  with  the  other  Oudin,  with  the 
water  rheotsat,  condenser  and  spark  gap.  The  primary  of  the 
Oudin  in  this  case  is  fixed  so  that  it  cannot  be  varied. 

To  light  the  lamp  between  two  persons,  let  one  person 


102  WIRELESS  TELEGRAPHY  AND 


Plate    IX,.       Photograph    illustrating    transformer    action    by    lighting 
lamp  in  the   secondary. 


HIGH  FREQUENCY  ELECTRICITY  103 

stand  on  the  insulating  stool  (see  Plate  VIII)  and  take  a  brass 
rod  in  one  hand.  Let  another  person  stand  on  the  ground. 
Let  the  person  on  the  stool  take  one  terminal  of  the  lamp 
in  one  hand  and  the  person  on  the  ground  grasp  the  other 
terminal  of  the  lamp.  Turn  on  the  current  and  approach  the 
rod  to  the  terminal  of  the  Oudin,  touching  the  terminal  of  the 
Oudin  with  the  rod.  The  lamp  will  light  up  to  full  candle 
power  if  everything  is  in  resonance  (see  Plate  VIII).  To  se- 
cure this  the  spark  gap  should  not  be  too  close  together  nor 
yet  too  far  apart.  Adjust  the  spark  gap  until  the  maximum 
result  is  obtained. 

This  bottle  Oudin  operates  Crooke's  tubes  and  Geisler 
tubes  beautifully.  Stand  on  the  insulating  stool,  taking  an 
aluminum  rod  in  one  hand  and  the  tube  in  the  other.  Set 
the  apparatus  to  going  and  touch  the  terminal  of  the  Oudin 
with  the  aluminum  rod.  The  tube  wi-11  light  up.  If  every- 
thing is  in  resonance,  the  tube  will  shine  brightly.  Wave  it 
back  and  forth  in  the  air.  Let  a  second  person  take  hold  of 
the  end  of  the  tube  and  then  touch  the  Oudin  with  the  rod. 
The  tube  will  shine  brightly.  Sparks  can  be  drawn  from  any 
part  of  the  body  of  the  operator  and  sparks  can  be  taken  on 
the  bare  hands  between  the  two  operators. 

Let  each  person  take  a  brass  rod  in  his  mouth.  Let  the 
one  on  the  stand  touch  the  Oudin  with  the  rod  and  let  the 
second  person  move  himself  near,  so  that  a  spark  can  pass 
between  the  brass  rods. 

All  of  this  phenomena  takes  place  without  the  operators 
feeling  anything,  except  when  the  sparks  are  taken  on  the  bare 
hand.  Then  the  discharge  stings  and  burns.  If  done  very 
much,  sores  will  be  formed  on  the  hands,  due  to  the  burns. 

Let  one  person  stand  on  the  insulating  stand  and  touch 
the  terminal  of  the  Oudin.  Let  another  person  take  a  vacuum 
tube  in  the  hand  and  walk  around  near  the  other.  The  tube 
will  light  up  several  feet  away.  The  more  powerful  the  ap- 
paratus, the  farther  away  the  tube  will  light.  We  have  suc- 
ceeded in  lighting  them  at  a  distance  of  6  feet. 

To  demonstrate  the  principles  of  the  transformer,  con- 
struct a  couple  of  coils  as  follows  (see  Plate  IX)  :  Make  one 


104  WIRELESS  TELEGRAPHY  AND 

coil  of  No.  12  rubber  covered  wire,  24  inches  in  diameter,  con- 
taining 7  turns.  Wind  these  turns  closely  together  irregularly 
and  tape  them  together,  allowing  the  free  ends  to  come  out 
within  4  to  6  inches  of  each  other.  Make  a  second  coil  of 
No.  16  rubber  covered  wire,  putting  4  turns  in  it.  Make  this 
24  inches  in  diameter,  and  tape  it  the  same  as  the  first.  This 
is  the  secondary.  Attach  an  ordinary  lamp  socket  to  the 
terminals  of  the  secondary.  Attach  the  primary  to  the  oscil- 
lation circuit  in  place  of  the  Oudin,  as  shown  in  Fig.  58. 
Tune  by  varying  the  condenser  and  water  rheostat.  Set  the 
current  to  oscillating  and  bring  the  secondary  near  the  pri- 
mary, a  110  16-candle-power  lamp  being  first  placed  in 
the  socket.  The  secondary  should  be  held  so  that  the  plane 
of  its  coil  is  parallel  to  the  plane  of  the  primary.  When  at 
the  right  distance,  the  lamp  will  light  up  without  having  any 
electrical  connection  with  the  primary.  Turn  the  secondary 
in  different  positions  and  note  the  results. 


HIGH  FREQUENCY  ELECTRICITY  105 

• 

CHAPTER  VII. 

AMATEUR   STATIONS   AND   SELECTIVE   TUNING. 

Many  boys  and  amateurs  are  establishing  wireless  tele- 
graph stations  in  every  section  of  the  United  States.  These 
stations  are  a  source -of  never-ending  delight  to  the  boy  who 
has  scientific  tastes. 

He  finds  here  a  means  within  his  reach,  by  means  of  which 
he  can  study  electricity  from  both  a  theoretical  and  a  practical 
standpoint.  The  mere  theoretical  study  of  scientific  subjects 
is  unsatisfactory.  One  reads  of  course  of  the  things  that  others 
have  done,  with  great  interest;  but  the  subject  remains  a 
mystery,  unless  one  can  become  familiar  with  it  by  actual  con- 
tact. 

Wireless  telegraphy  furnishes  &  means  for  that  contact, 
and  that  is  why  it  is  becoming  so  popular  with  many  people. 
It  furnishes  an  avenue  along  which  a  boy  may  expend  his 
leisure  time,  much  to  his  profit  and  enlightenment. 

Los  Angeles  has  its  share  of  boys  whose  minds  turn 
toward  the  natural  phenomena  of  nature.  Electricity  is  fas- 
cinating to  all  boys,  and  wireless  telegraphy  gives  them  the 
opportunity  to  become  familiar  with  alternating  current  phe- 
nomena at  a  small  cost.  This  is  of  immense  practical  value 
to  them,  because  the  phenomena  of  wireless  telegraphy  is  the 
phenomena  of  the  commercial  alternating  current,  and  the 
knowledge  they  obtain  here  wrill  be  of  great  value  to  them  in 
the  electrical  field  of  the  commercial  world. 

When  so  many  stations  are  operating,  interference  be- 
comes serious ;  and  this  problem  of  interference  must  be 
solved  before  wireless  telegraphy  or  telephony  can  possibly 
become  a  commercial  success. 

If  the  wireless  companies  now  in  the  field  were  doing  a 
large  business,  it  would  be  necessary  for  each  company  to 
occupy  the  field  all  of  the  time,  night  and  day.  Under  pres- 
ent conditions,  only  one  sending  station  can  operate  at  a  time. 
When  one  station  is  sending,  all  stations  far  and  near  are 


106  WIRELESS  TELEGRAPHY  AND  ' 

affected  by  the  waves  sent  out  by  that  station,  and,  if  the  sta- 
tion is  a  strong  one,  no  other  station  can  receive  any  one 
except  the  sending  station. 

If  five  stations  are  sending  in  the  same  region,  then  every 
station  that  is  not  sending  hears  in  his  telephone  a  confused 
buzz,  the  result  of  the  mixture  of  the  waves  of  all  of  the 
sending  stations.  If  one  of  the  sending  stations  has  a  tone 
to  its  buzz  radically  different  from  all  of  the  others,  the  skill- 
ful operator  can  pick  out  that  particular  one  and  read  it. 

If  some  of  the  sending  stations  are  weaker  than  others, 
owing  to  distance  or  to  low  power,  then  the  strongest  signal 
can  be  read.  If  a  dozen  people  are  talking  all  at  once  in  a 
room,  one  can  pay  attention  to  one  of  them  and  understand 
what  he  is  saying,  even  though  the  others  are  talking. 

The  solution  of  interference  is  not  to  be  found  by  driving 
the  amateurs  out  of  the  field.  It  would  be  very  unfortunate, 
indeed,  if  our  Congress  were  to  take  action  giving  a  monopoly 
of  the  space  above  and  about  us  to  any  corporation  or  set  of 
corporations.  The  development  of  aerial  navigation  and  wire- 
less telegraphy  demands  that  the  air,  the  same  as  the  surface 
of  the  ocean,  be  kept  a  public  highway. 

Selective  tuning  offers  a  complete  solution  of  this  problem. 

For  selective  tuning,  undamped  continuous  waves  are 
necessary.  Condenser  discharges  at  the  frequencies  now  in 
use  give  a  train  of  damped  oscillations  as  shown  in  Fig.  /p. 
No  selective  tuning  can  be  effected  on  a  wave  of  this  nature. 

Continuous  undamped  waves,  like  those  in  Fig.  60,  are 
necessary.  These  undamped  waves  would  give  an  effect  like 
that  in  Fig.  84.  If  these  waves  could  be  rectified  as  in  Fig.  dp, 
a  still  better  effect  might  be  produced. 

It  will  be  observed  that  in  Fig.  79  there  is  considerable 
distance  between  the  maximum  value  of  each  discharge.  This 
leaves  a  blank  between  the  discharges.  The  higher  the  fre- 
quency, the  smaller  this  blank. 

Referring  to  Fig.  84,  it  will  be  seen  that  there  is  a  blank 
interval  between  the  maximum  value  of  the  continuously 
sustained  oscillations.  If  these  oscillations  could  be  rectified, 
a  greater  effect  would  be  produced. 


HIGH  FREQUENCY  ELECTRICITY  107 

The  higher  the  frequency,  the  closer  the  maximum  values. 
This  high  frequency  produces  a  short  wave  length.  Fes- 
senden  has  solved  the  prqblem  of  selective  tuning  by  the 
use  of  a  high  frequency  alternator.  Poulsen  and  The  Collins 
Wireless  Telegraph  Company  have  solved  the  problem  by  use 
of  the  direct  current  arc. 

I  do  not  maintain  that  the  amateur  should  be  allowed 
to  obstruct  the  growth  of  wireless  telegraphy.  He  is  not  do- 
ing so.  He  is  in  fact  advancing  its  interests.  If  no  amateurs 
were  in  the  field,  the  problem  would  be  just  as  serious,  because 
only  one  station  of  only  one  company  could  work  in  the  same 
region  at  a  time,  and  this  fact  alone  would  render  wireless 
telegraphy  useless  commercially. 

The  amateur  is  then  only  bringing 'to  the  front,  more 
forcibly,  the  necessity  for  selective  tuning.  If  selective  tun- 
ing is  impossible,  the  only  remedy  is  government  ownership 
of  wireless,  not  for  commercial  use,  but  for  the  uses  to  which 
it  is  now  putting  it. 

Wireless  telegraphy  and  telephony  have  no  commercial 
use  unless  selective  tuning  is  possible.  Theoretically,  selective 
tuning  is  possible,  and  there  are  two  commercial  companies 
in  the  field  today  in  the  United  States,  who  claim  to  have 
solved  it. 

The  Collins  Wireless  Telephone  Company  claims  to  have 
solved  selective  tuning  to  such  an  extent  that  they  can  work 
beside  the  most  powerful  wireless  telegraph  stations,  abso- 
lutely without  interference. 

The  company  that  owns  the  Fessenden  patents  claims  to 
have  accomplished  the  same  thing  for  wireless  telegraphy. 
The  time  is  close  at  hand  when  these  companies  will  demon- 
strate what  they  can  do  in  this  line.  Selective  tuning  thus 
solves  the  difficulty  without  driving  any  one  off  the  public 
domain. 

Tuning  is  possible  with  the  circuits  given  in  this  book. 
If  stations  differ  radically  in  their  wave  length,  they  can  be 
received  on  different  parts  of  the  closed  oscillation  circuit, 
and  in  this  case,  when  one  is  coming  in  loud,  the  other  is 
coming  in  weak. 


108 


WIRELESS  TELEGRAPHY  AND 


Plate  X.     Photograph  of  interior  of  station  at  the  Los  Angeles  Poly- 
technic High  School.     Sending  outfit  on  the  right. 
Receiving  set  in  the  center. 


HIGH  FREQUENCY  ELECTRICITY 


109 


Fig.    59.      Receiving    circuit.      Non-inductive.      Excellent    for    tuning 

out  short  waves. 

Fig-  59  is  an  excellent  circuit  for  this  purpose.  Mr.  Far- 
ran  tried  this  circuit  for  the  first  time,  some  few  days  ago, 
and  found  it  to  be  excellent,  not  only  for  tuning  out  near-by 
stations  with  short  wave  lengths,  but  also  for  bringing  in 
distant  long  wave  stations  strongly.  We  had  been  using  the 
Shoemaker  connections  shown  in  Fig.  32  with  excellent  results, 
but  it  is  not  very  selective. 

In  the  connections  shown  in  Fig.  59,  the  closed  oscillation 
circuit  AOCD  is  joined  to  the  looped  aerial  EIB  by  a  movable 
contact  E  and  a  fixed  point  B.  B  is  attached  at  the  junction 
of  the  condenser  and  the  inductance.  D  is  the  detector  around 
which  the  telephone  should  be  shunted.  F  is  a  movable  con- 
tact for  the  ground.  The  condenser  C  is  adjustable. 

"\Vhen  E  and  F  are  in  the  middle  of  the  tuning  coil,  all 
short  waves  ground  and  become  very  weak  or  silent  entirely. 
All  long  waves  set  up  oscillations  in  the  closed  circuit.  With 
this  arrangement  we  were  able  to  tune  out  the  boys  in  near-by 
stations  and  read  TM,  the  government  station  at  Point  Loma, 
Cal.,  100  miles  away,  or  PI,  the  United  Wireless  station  at 
Catalina,  fifty  miles  away. 

The  station  on  the  Polytechnic  High  School  was  estab- 
lished in  the  fall  of  1908.  It  is  stretched  horizontally,  between 
the  science  hall  on  20th  St.,  and  the  main  building  on  Wash- 


110 


WIRELESS  TELEGRAPHY  AND 


Plate  XL     Photograph  of  one  end  of  the  aerial  on  the  Los  Angeles 
Polytechnic   High   School,   roof   of   Science    Hall. 


HIGH  FREQUENCY  ELECTRICITY  111 

ington  St.  It  is  about  35  feet  from  the  ground  at  one  end  and 
50  feet  at  the  other,  being  20  feet  above  the  roof  of  the  build- 
ing part  of  the  way,  and  30  feet  the  rest  of  the  way.  It 
points  north  and  south.  The  aerial  is  composed  of  four" 
strands  of  No.  12  aluminum  bare  wire,  200  feet  long.  They 
are  joined  together  at  the  Washington  St.  end  and  are  brought, 
side  by  side,  about  2  feet  apart,  to  a  pole  on  top  of  the  science 
hall.  Here  two  leads  are  brought  down  into  the  office  through 
a  skylight.  One  lead  comes  from  two  of  the  wires  on  one  side, 
and  the  other  lead  comes  from  the  two  wires  on  the  other  side. 

The  20th  St.  end  is  shown  in  Plate  XI,  and  the  interior 
is  shown  in  Plate  X.  The  aerial  thus  has  800  feet  of  wire  in 
parallel.  There  are  two  leads  60  feet  long.  This  makes  720 
feet  of  wire  in  the  aerial.  The  aerial  can  thus  be  used  as  a 
looped  one  or  otherwise,  as  desired. 

The  receiving  instruments  are  similar  to  those  described 
in  this  book,  and  they  are  connected  as  shown  in  Fig.  59  or 
Fig.  32.  The  detectors  used  are  silicon,  iron  pyrite  or  perikon. 
The  best  work  has  been  done  with  the  pyrite.  The  perikon 
is  very  sensitive,  but  not  as  reliable  as  the  pyrite.  The  Col- 
lins 2,000-ohm  receivers  are  used  with  no  potentiometer  or 
battery.  A  75-ohm  Bell  telephone  is  also  used  that  is  very 
sensitive. 

In  the  sending,  a  1 -kilowatt  transformer  is  used,  giving 
20,000  volts  on  the  high  side.  The  Massie  connections  are 
used  for  a  hook-up.  With  this  outfit,  Mr.  Farran  has  been  able 
to  send  as  far  south  as  San  Diego  and  out  to  sea  far  north  of 
Santa  Barbara,  covering  100  miles  south  and  at  least  180  miles 
north.  This  was  done  on  2l/2  amperes  in  the  primary  of  the 
transformer.  The  current  was  cut  down  with  a  water  rheo- 
stat and  only  a  3/10  inch  spark  was  used. 

The  ships,  communicated  with,  read  us  with  ease  and  said 
that  the  station  came  in  strong  and  clear.  This  means,  of 
course,  that  the  station  was  reaching  much  farther,  but  we 
have  not  been  able  to  test  to  farther  distances.  • 

In  receiving  we  have  been  able  to  hear  the  U.  S.  warships 
in  Magdalena  Bay,  725  miles  in  an  air  line  south,  and  Table 
Bluff,  560  miles  north. 


112 


WIRELESS  TELEGRAPHY  AND 


Plate  XII      Photograph  of  .station  of  the  Southern  Pacific  Telegraph 
School,  542  Central  Ave.     Apparatus  made  by  a  Los  Angeles  boy. 


HIGH  FREQUENCY  ELECTRICITY  113 

W.e  have  thus  been  able  to  work  with  ships  at  sea  both 
receiving  and  sending,  to  a  distance  of  at  least  180  miles, 
using  in  sending  only  2j/2  amperes.  The  aerial  tunes  on  this 
many  amperes.  We  are  able  to  get  the  Farallones  and  the 
San  Francisco  stations  at  night,  368  miles  north  in  an  air 
line.  Magdalena  Bay  was  received  in  the  daytime,  but  Table 
Bluff  at  night. 

Mr.  Roy  Zoll  was  the  first  boy  to  install  a  sending  and 
receiving  outfit  in  the  city,  so  far  as  I  know.  Mr.  J.  T.  LaDu 
and  myself  had  installed  small  sending  outfits  some  time 
previously. 

Prior  to  this  time  there  were  some  receiving  stations,  but 
none  equipped  with  sending  instruments.  We  used  power 
transformers  from  the  first. 

Mr.  Zoll's  first  aeria]  consisted  of  two  baskets,  27  feet 
long,  strung  up  on  a  75-foot  pole.  Each  basket  had  four  No. 
18  copper  wires  in  it,  arranged  around  circular  hoops  1  foot 
in  diameter.  The  two  baskets  were  2]/2  feet  apart.  With 
this  vertical  aerial  and  a  carborundum  detector,  he  was  able 
to  hear  the  fleet  of  sixteen  battleships  on  their  trip  up  from 
Magdelena  Bay  in  April,  1908,  long  before  they  reached  San 
Diego. 

Mr.  Zoll's  station  is  located  on  the  top  of  a  hill.  His 
pole  is  made  of  a  eucalyptus  tree,  75  feet  high.  He  used 
ordinary  Bell  telephone  receivers.  Point  Loma  and  the  United 
Wireless  station  in  San  Diego,  the  San  Francisco  stations  and 
the  Farallones  were  all  picked  up  by  him  before  any  of  the  rest 
of  us  heard  them.  Some  time  later  he  added  to  these  baskets 
two  loops  each,  containing  three  wires  70  feet  long.  These 
branches  were  joined  together  at  the  top,  and  they  spread 
apart  64  feet  at  the  bottom.  With  this  aerial  his  range  was 
considerably  increased.  He  was  able  to  receive  the  following 
stations,  besides  those  already  heard :  SV,  Tatoosh  Island, 
Washington;  and  SP,  Navy  Yard,  Puget  Sound,  1,000  miles 
north. 

Later  he  stretched  three  wires  160  feet  horizontally  from 
the  top  of  his  pole  to  another  pole,  and  stretched  two  radiat- 


114  WIRELESS  TELEGRAPHY  AND 

ing  wires  from  this,  one  140  feet  long  and  the  other  180  feet 
long,  making  in  all  1,320  feet  of  wire. 

After  the  first  change  iron  sulphide  was  used  as  a  detector. 
With  this  aerial  he  heard  the  West  Virginia  at  Magdalena 
Bay,  725  miles  south. 

Mr.  A.  E.  Abrams  was  among  the  first  to  install  a  receiv- 
ing and  transformer  sending  outfit.  His  pole  is  71  feet  high. 
It  is  on  the  top  of  his  house.  The  aerial  consists  of  four  wires 
75  feet  long,  of  No.  18  bare  copper  wire.  The  spreaders  are 
Wy2  feet  long. 

His  transformer  is  a  350-watt.  The  primary  consists  of 
four  layers  containing  166  turns,  tapped  at  five  points.  His 
secondary  has  75,000  turns  of  No.  36  D.S.C.  The  coils  are 
y%  inch  thick  with  ^  inch  space  between  them.  The  iron  core 
is  \6l/2  inches  by  Sl/2  inches,  with  a  cross  section  of  2l/2  square 
inches. 

In  receiving  he  has  heard  as  far  north  as  Cape  Blanco  and 
south  of  San  Diego. 

Mr.  D.  Whiting  of  627  St.  Paul  St.,  located. on  the  hills, 
has  a  pole  120 -feet  high.  The  aerial  is  140  feet  long,  contain- 
ing six  wires,  arranged  in  a  loop  system.  The  leads  are  60 
feet  long.  He  uses  a  2-kilowatt  transformer  of  40,000  volts. 
The  iron  in  the  transformer  is  ordinary  sheet  iron.  •  DeForest 
connections  are  used  in  the  sending. 

His  receiving  sets  are  connected  according  to  the  Shoe- 
maker and  Massie  systems.  He  has  a  pair  of  Collins  Wireless 
telephones  and  uses  silicon,  iron  pyrites,  perikon  and  electro- 
lytic detectors. 

He  has  been  able  to  receive  as  far  north  as  Tatoosh,  1,000 
miles,  and  as  far  south  as  Magdalena  Bay,  725  miles. 

The  Southern  Pacific  Telegraph  School,  542  Central  Ave., 
has  a  wireless  station.  The  aerial  is  a  horizontal  one,  65  feet 
high  at  one  end  and  45  on  the  other.  It  is  composed  of  10  strands 
of  No.  12  copper  wire.  They  are  all  connected  together  at  the 
upper  end  and  brought  in  to  the  instruments  at  the  other  end 
by  one  lead.  They  have  a  1-kilowatt  transformer  and  appara- 
tus made  by  a  Los  Angeles  boy.  Plate.  XII  is  a  view  of  their 
sending  and  receiving  outfits.  This  school  is  owned  and  man- 


HIGH  FREQUENCY  ELECTRICITY  115 

aged  by  Mr.  F.  D.  Mackay.  Facilities  are  presented  here  for 
a  training  in  railroad  telegraphy,  commercial  telegraphy  and 
wireless  telegraphy. 

Plate  XIII,  is  a  photograph  of  the  author's  station.  The 
house  is  35  feet  high  and  the  pole  is  40  feet  high,  thus  giving 
75  feet  above  the  ground.  Aerials  of  various  kinds  have  been 
tried.  The  one  now  in  operation  is  as  it  appears  in  the  cut, 
with  the  exception  of  a  small  wire  which  connects  all  of  the 
guy  wires  together.  This  wire  was  too  small  to  photograph. 
There  are  in  all  twelve  guy  wires,  although  only  ten  can  be 
seen  in  the  cut.  Two  of  them  are  so  nearly  in  line  with  the 
pole  as  to  be  invisible. 

Three  of  them  are  85  feet  long,  four  of  them  35  feet  and 
five  of  them  50  feet  long.  This  gives  a  total  length  of  645 
feet.  They  are  all  connected  together  at  the  base  and  a  lead 
is  brought  in  to  the  instruments.  They  are  all  thoroughly  in- 
sulated from  the  pole,  the  house  and  the  ground  and  are  un- 
connected at  the  top.  Provision  is  made  also  for  swinging 
up  any  kind  of  an  aerial  besides.  The  lead  wire  goes  in  at 
the  rear  of  the  building. 

The  guy  wires  themselves,  however,  form  such  a  good 
aerial  as  to  make  another  unnecessary.  With  these  guy  wires 
and  the  use  of  2l/2  amperes,  we  have  been  able  to  send  to 
Catalina,  50  miles  away,  and  San  Diego,  100  miles  away.  In 
receiving  we  have  heard  all  of  the  San  Francisco  stations  at 
night,  365  miles  awray.  We  have  also  heard  the  warships  in 
San  Francisco  Bay. 

We  have  used  a  166-watt  transformer  and  a  kilowatt 
transformer  at  this  station.  We  used  a  Collins  2,000-ohm  tele- 
phone and  a  very  sensitive  Bell  telephone  receiver  of  75  ohms 
resistance.  The  detectors  used  were  carborundum,  silicon  and 
iron  pyrites.  Our  best  work  was  done  with  iron  pyrites. 


116 


WIRELESS  TELEGRAPHY  AND 


Plate    XIII.      Photograph    of    the    aerial    on    the    author's    residence. 
Guy  wires  used  as  an  aerial. 


HIGH  FREQUENCY  ELECTRICITY  117 

CHAPTER  VIII. 

.  NATURE  OF  ELECTRICITY. 

1.  Energy. — Electricity  is  a   form   of  energy,   and   since 
all  forms  of  energy  are  forms  of  matter  in  motion,  we  are 
justified    in    saying    that    electricity    must    be    some    form    of 
moving  matter. 

The  hand  in  motion  is  one  kind  of  energy;  the  air  in  mo- 
tion, water  in  motion,  and  a  bullet  in  motion  are  forms  of 
energy. 

All  forms  of  energy  with  which  we  are  thoroughly  ac- 
quainted have  just  two  factors,  mass  and  motion,  nothing  else. 
In  the  kinds  mentioned  above,  the  energy  is  conveyed  from  one 
place  to  another  by  the  mass  moving  bodily  from  one  place 
to  another,  where  it  delivers  up  its  motion  to  whatever  it 
comes  in  contact  with,  and  in  the  proportion  that,  it  gives 
its  motion  to  some  other  form  of  matter  it  must  lose  motion. 
This  is  one  way  of  transmitting  motion  from  one  place  to 
another. 

2.  Waves. — In  the  ocean  the  wind  blows  upon  the  sur- 
face of  the  water  hundreds  of  miles  out  at  sea.     The  water 
is   depressed   under  the   pressure   of  the   moving  air.     When 
the  pressure  of  the  wind  is  relaxed,  the  water  is  pressed  up- 
ward by  the  pressure  of  the  higher  water  around  it,  but,  in- 
stead of  coming  to  rest,  it  shoots  upward  beyond  the  level 
of  the  surface  of  the  still  water.     This  is  due  to  the  fact  that 
when  once  in  motion  it  must  keep  on  moving  until  something 
takes  its  motion  away  from  it.     Consequently  a  hollow  and  a 
crest  are  formed.     The  water  in  the  crest  now  falls  and  the 
water  in  the  trough  is  pressed  upward  as  before,  thus  setting 
up   a   vibratory   motion    in   the    water.      While   this   is   going 
on,   however,   a   wave   is   sent  out   through   the   water  and  a 
succession  of  crests  and  hollows  is  formed. 

Now  while  the  water  simply  moves  up  and  down,  the 
wave  motion  goes  forward  over  the  surface  of  the  wrater  for 
hundreds  of  miles.  If  the  wind  keeps  blowing,  the  waves  will 


118  WIRELESS  TELEGRAPHY  AND 

keep  on  coming  and  a  ship  hundreds  of  miles  from  the  storm 
will  be  raised  and  lowered  by  the  waves  running  under  it. 

This  is  another  way  of  transmitting  motion.  These  are 
called  transverse  waves.  The  wind  is  a  form  of  moving  mat- 
ter which  we  may  call  wind  energy.  This  moving  air  sets  the 
water  to  moving  up  and  down.  We  will  call  this  water  en- 
ergy. This  vibrating  water  sets  up  a  wave  motion  in  the 
water  and  the  wave  travels,  but  the  water  rnerely  rises  up 
and  down. 

This  wave  is  a  form  of  matter  in  motion  also,  but  it  is  not 
the  matter  that  travels.  The  motion  is  given  by  one  set  of 
particles  vibrating  up  and  down  to  other  particles,  which  are 
caused  to  vibrate  up  and  down  and  the  motion  is  thus  trans- 
mitted long  distances  where  the  water  can  deliver  it  to  some 
other  kind  of  matter. 

A  wave  motor,  for  instance,  consisting  of  a  float  which  is 
caused  to  work  machinery  by  its  rise  and  fall  can  compress 
air.  This  compressed  air  can  be  used  to  run  a  dynamo,  etc. 
Now  through  all  this  we  have  merely  changes  of  motion  from 
one  kind  of  matter  to  another  kind  of  matter,  and  it  is  the 
motion  that  is  transmitted. 

c 


Fig.  60.     Sine  curve. 

Fig.  60  is  an  illustration  of  this.  AD  is  called  a  wave 
length  and  AB  is  half  a  wave  length.  A,  B  and  D  are  called 
nodes  in  the  wave.  C  is  the  crest  of  the  wave  and  the  lowest 
part  of  the  wave  is  the  trough  of  the  wave.  The  distance  from 
the  crest  of  the  wave  to  the  trough  of  the  wave  measured  per- 
pendicular to  AD  is  the  amplitude  of  the  wave.  The  number 
of  complete  waves  formed  per  second  is  called  its  frequency. 


HIGH  FREQUENCY  ELECTRICITY  119 

If  C  falls  to  the  trough  and  back  again  in  one  second,  the 
wave  has  a  frequency  of  a  second  and  one  wave  is  formed  per 
second.  If  C  makes  two  swings  per  second,  two  waves  will 
be  formed  in  a  second.  If  three  oscillations  are  executed, 
three  wave  lengths  will  be  formed  in  a  second,  and  the  wave 
will  have  a  frequency  of  three  per  second.  The  waves  thus 
become  shorter  as  the  frequency  grows  larger. 

3.  Light. — Light  comes  to  us  from  the  sun  and  the  stars. 
For  a  long  time  the  nature  of  light  was  not  known.     Newton 
thought  it  to  be  a  stream  of  corpuscles  or  little  bodies  shot 
out  in  all  directions  from  the  sun,  but  later  it  was  shown  to 
be  due  to  waves  like  the  waves  in  the  ocean.    This  was  proved 
to  be  so,  and  hence  the  motion  going  on  in  the  sun  is-  not 
brought  to  us  by  a  stream  of  bullets,  but  by  a  wave  which 
is  set  up  in  the  sun  by  some  vibrating  form  of  matter.     The 
only  thing  that  can  set  up  waves  like  those  in  the  water  is 
some  form  of  matter  that  is  vibrating  back  and  forth.    In  order 
to  have  waves  there  must  be  something  in  which  to  set  up  the 
wave. 

4.  Ether. — Therefore  men  have  concluded  that  all  space 
is  filled  with  a  form  of  matter  to  which  the  name  of  ether  is 
given. 

This  ether  is  made  up  of  very  fine  particles  so  minute  that 
it  is  useless  to  write  down  the  figures  which  express  their 
size.  These  particles  have  a  very  minute  mass  and  they  are 
vibrating  with  exceeding  swiftness.  Thus  the  earth,  the  sun 
and  the  stars  are  immersed  in  an  ocean  of  matter  through 
which  they  are  all  moving. 

There  is  no  such  thing  as  matter  without  motion.  As 
you  sit  in  your  chair  reading  you  seem  to  be  sitting  still  and 
the  room-  about  you  seems  to  be  still,  but  you  are  deceived. 
The  particles  of  the  body,  of  the  wood  and  of  everything 
about  you  are  vibrating  swiftly. 

5.  Molecules  and  Atoms. — These  little  particles  are  called 
molecules,  and  their  motion  of  vibration  is  called  heat.     Thus 
heat  is  a  form   of  energy,  and  it  consists  of  little  bodies  of 
matter  in  motion.    These  molecules  are  very  minute,  but  th?y 


120  WIRELESS  TELEGRAPHY  AND 

are  in  turn  formed  by  a  collection  of  still  smaller  bodies  called 
atoms.  The  atoms  were  supposed  to  be  the  smallest  particles 
of  matter  that  could  exist  alone,  when  they  were  first  dis- 
covered. The  word  atom  means  uncut,  indivisible,  and  that 
name  was  given  to  them  because,  at-  that  time,  no  finer  form 
of  matter  was  known  and  the  chemists  of  that  time  could  not 
divide  them  into  finer  forms.  Until  recently  man  was  not  able 
to  show  that  the  atom  is  divisible. 

6.  Corpuscles  or  Electrons. — However,  J.  J.  Thomson 
and  others  have  shown  that  electricity  is  made  of  little  par- 
ticles of  matter,  and  these  little  particles  have  a  mass  that  is 
somewhere  near  Vaooo  the  mass  of  the  hydrogen  atom.  It  was 
by  means  of  the  phenomena  presented  by  radium,  the  X-ray 
and  Crooke's  tubes  .that  they  were  able  to  do  this.  These 
little  bodies  are  called  corpuscles  or  electrons.  J.  J.  Thomson 
supposes  these  corpuscles  to  be  little  bodies  that  carry  nega- 
tive charges  of  electricity. 

It  is  much  simpler  to  call  these  little  corpuscles  electricity 
than  to  call  them  bodies  carrying  electricity,  because  the  one 
is  just  as  probable  as  the  other;  since  electricity  in  its  final 
analysis  has  to  come  down  to  some  form  of  matter  in  motion, 
we  might  just  as  well  call  these  corpuscles  electricity,  until 
it  is  shown  that  electricity  is  some  still  finer  form  of  matter. 
The  corpuscles  themselves  are  supposed  to  be  made  up  of 
whorls  of  ether  particles.  Certain  particles  of  the  ether  are 
grouped  together  and  move  together  in  a  whorl,  thus  rare- 
fying the  ether  at  that  point.  Then  if  the  atom  is  made  of  the 
corpuscles,  ordinary  coarse  matter  is  a  rarefication  in  the  ether 
and  the  ether  is  very  dense,  although  the  particles  of  which 
it  is  formed  are  very  minute,  having  exceedingly  small  mass. 

On  account  of  the  fact  that  electricity  can  be  produced 
from  all  forms  of  matter  by  friction,  it  was  early  recognized  that 
electricity  is  present  in  all  forms  of  matter.  The  phenomena  of 
the  Crooke's  tubes  has  shown  that  radiant  energy  consists  of 
a  stream  of  these  corpuscles,  and,  from  this  and  other  phe- 
nomena, it  has  been  shown  that  these  little  bodies,  constituting 
the  negative  electricity,  come  from  the  atom.  •  It  is  thus  shown 


HIGH  FREQUENCY  ELECTRICITY 


121 


that  the  atoms  are  at  least  made  up  of  corpuscles  as  one  of 
their  constituent  factors. 


Fig.  61.     Relative  size  of  the  atom  and  the  corpuscles. 

In  Fig.  61  let  B  represent  a  hydrogen  atom.  These  atoms 
are  so  minute  that  it  takes  trillions  of  them  placed  side  by  side 
to  make  a  line  an  inch  long.  If  this  represents  one  atom,  then 
we  have  it  enormously  magnified.  Suppose  little  dots  A  to 
be  corpuscles.  If  the  whole  circle  were  filled  with  these  dots 
as  thickly  as  they  exist  at  A,  then  there  would  be  2,000  of 
them  in  the  circle.  The  oxygen  atom  would  have  sixteen  times 
as  many  and  other  atoms  of  the  elements  as  many  more,  de- 
pending upon  their  atomic  weights. 

Whenever  electricity  is  generated,  these  corpuscles  are 
torn  loose  from  the  atoms  and  either  collected  on  insulating 
surfaces  or  sent  streaming1  through  a  conductor ;  as  soon  as  they 
lose  the  motion  communicated  to  them  by  the  generating  ma- 


122  WIRELESS  TELEGRAPHY  AND 

chine  or  battery,  they  return  again  to  the  atom  and  cease  to 
manifest  themselves  to  us. 

7.  Ether  Waves. — Three  kind  of  waves  are  known  to 
exist  in  that  great  ocean  of  matter,  the  ether ;  and  these  waves 
are  set  up  by  any  source  of  energy  such  as  the  sun  and  the 
stars.  What  is  it  vibrating  in  the  sun  that  causes  these 
waves?  They  all  travel  with  the  same  speed,  186,500  miles 
per  second,  or  300,000  kilometers  per  second. 

The  waves  that  affect  the  eye  are  called  light  waves.  The 
wave  length  of  light  has  been  measured  and  has  been  found 
to  range  from  .000076  of  a  centimeter  for  the  extreme  red  to 
.000038  of  a  centimeter  for  the  extreme  violet. 

The  heat  waves  affect  all  parts  of  the  body,  causing  the 
molecules  to  vibrate  more  rapidly.  This  causes  the  nerves  to 
vibrate  and  \ve  have  a  sensation  which  we  call  heat.  The 
longest  heat  waves  measured  are  .006  centimeters  long.  Heat 
waves  are  thus  found  below  .000038  centimeters  and  not  above 
.006  centimeters  long.  When  the  waves  become  longer  than 
.006  they  cease  to  deliver  up  their  motion  to  the  molecules  and 
thus  cease  to  be  heat  waves  and  become  what  is  known  as 
electromagnetic  waves. 

These  last  kind  of  waves  range  from  .3  of  a  centimeter 
long  up  to  many  miles  long.  The  longer  the  wave,  the  less 
ordinary  matter  interferes  with  it.  All  conductors,  however, 
interfere  with  these  long  waves.  Hertz  showed,  by  a  series 
of  experiments,  that  light  waves,  heat  waves  and  electromag- 
netic waves,  are  the  same  thing,  differing  only  in  wave  length, 
and  Maxwell  proved  the  same  thing  mathematically. 

The  existence  of  free  corpuscles  in  the  sun  has  lately 
been  demonstrated  at  the  solar  observatory  on  Mt.  Wilson, 
near  Los  Angeles,  Cal. 

Dr.  George  Ellery  Hale,  in  a  lecture  delivered  at  Blanch- 
ard  Hall,  before  the  Academy  of  Sciences,  in  Los  Angeles, 
showed  photographs  of  sun  spots  in  both  the  northern  and 
southern  hemispheres  of  the  sun.  These  pictures  showed 
clearly  that  the  sun  spots  are  cyclonic  storms  in  the  sun's 
atmosphere.  The  storms  rotated  one  way  south  of  the  equator 
and  the  opposite  way  north  of  the  equator. 


HIGH  FREQUENCY  ELECTRICITY  123 

By  means  of  the  spectroscope  it  was  also  shown  at  the 
same  observatory  that  strong  magnetic  fields  exist  in  the  cen- 
ter of  these  sun  spots.  Now  the  only  thing  that  can  set  up 
magnetic  fields  are  corpuscles  moving  in  the  same  direction. 
Hence,  Dr.  Hale  concluded  that  free  corpuscles  exist  in  the 
atmosphere  of  the  sun,  and  when  sun  spots  are  formed,  they 
are  whorled  about  with  the  rest  of  the  matter  constituting  the 
atmosphere  of  the  sun. 

The  sun  is  sa  hot  that  these  corpuscles  can  exist  there  in 
a  free  state.  They  have  too  much  motion  to  allow  them  either 
to  stay  in  the  atoms  or  to  group  together  to  form  new  atoms. 

By  putting  two  and  two  together,  it  is  safe  to  form  the 
conclusion  that  these  waves  in  the  ether  are  caused  solely  by 
the  motion  of  these  corpuscles  of  electricity. 

If  the  corpuscle  moves  slowly  or  oscillates  slowly,  it  forms 
the  electromagnetic  wave ;  if  it  oscillates  rapidly  enough,  it 
forms  the  heat  wave ;  and  if  it  oscillates  still  more  rapidly,  it 
produces  the  light  wave. 

A  corpuscle  oscillating  back  and  forth  in  an  aerial  is  mov- 
ing comparatively  slow,  and  hence  it  sets  up  an  electromag- 
netic wave  in  the  ether.  If  it  were  caused  to  oscillate  much 
more  rapidly,  the  wire  of  the  aerial  would  become  hot  and 
heat  waves  would  result ;  if  it  were  caused  to  oscillate  at  a 
very  high  speed,  the  wire  would  become  white  hot  and  light 
waves  would  be  emitted. 

Thus  when  ordinary  molecular  matter  is  heated  suf- 
ficiently, the  corpuscles  in  the  atoms  are  made  to  vibrate  more 
violently  and  they  thus  set-up  waves  in  the  ether. 

If  the  rate  of  vibration  is  low,  they  produce  electromag- 
netic waves;  if  still  higher,  heat  waves;  and  if  still  higher, 
light  waves. 

8.  Resistance. — By  experiment  it  is  found  that  some  sub- 
stances conduct  electricity  easily  and  others  do  not.  Since  the 
electric  current  is  a  stream  of  corpuscles,  we  can  imagine 
that  the  atoms  and  molecules  of  a  conductor  obstruct  their 
passage  through  the  wire.  They  stand  in  their  way,  and  the 
corpuscles  knock  against  them  and  have  to  go  around  them  in 


124  WIRELESS  TELEGRAPHY  AND 

their  passage   through.     This   is   called  the   ohmic   resistance 
of  the  wire  and  it  is  usually  designated  by  R. 

9.  Force. — All  forms  of  matter  in  motion  can  exert  pres- 
sure when  they  strike  other  forms  of  matter.     This  pressure 
is  called  a  force.     Force,  then,  can  be  denned  as  a  pressure 
exerted  by  moving  matter. 

All  forces,  the  nature  of  which  we  know,  are  due  to  pres- 
sure exerted  by  matter  in  motion.  The  wind  can  exert  a  force. 
Falling  or  flowing  water  can  exert  a  force.  Steam,  composed 
of  molecules  of  water  vibrating  very  rapidly,  can  exert  a  ter- 
rific pressure,  or  force.  All  these  are  examples  of  known 
forces. 

Gravitation,  cohesion  and  adhesion  are  examples  of  forces, 
the  nature  of  which  are  totally  unknown  to  us.  They  are  as- 
sumed to  be  attractions.  Nobody  has  ever  proved  this,  how- 
ever. Newton  assumed  that  gravitation  was  due  to  attraction 
and  everybody  since  that  time  has  assumed  it,  but  Newton  did 
not  prove  it,  nor  has  anybody  since  Newton's  time  proved  it. 

Since  all  known  forces  are  due  to  pressures,  it  is  quite  safe 
to  assume  that  gravitation,  cohesion  and  adhesion  are  also  due 
to  motions  in  the  ether,  whereby  bodies  made  of  corpuscles, 
atoms  and  molecules  are  pressed  together  by  virtue  of  their 
interference  with  the  vibrating  ether. 

10.  Voltage. — Electricity  in  motion  can  exert  a  pressure. 
This  pressure  is  called  its  voltage,  or  its  electromotive  force. 
It  is  usually  represented  by  E.     A  current  flowing  through  a 
wire,  then,  exerts  a  pressure.    It  also  requires  a  pressure  exerted 
by  something  to  make  a  current  flow  in  a  wire.     In  order  to 
understand  this,  we  must  know  what  is  taking  place  in  the 
ether  when  a  current  is  flowing  in  a  wire. 

5 
C  D  E 


TV- 
Fig.  62.     Lines  of  force  around  a  wire  carrying  a  current. 


HIGH  FREQUENCY  ELECTRICITY  125 

Although  electromagnetic  waves  can  be  set  up  in  the 
ether,  corpuscles  of  electricity,  by  themselves,  have  no  power 
of  making  their  way  through  it.  The  ether  seems  to  be  an 
absolutely  non-conductor  of  electricity ;  in  other  words,  the 
ether  offers  an  immense  resistance  to  the  movement  of  cor- 
puscles through  it,  but  when  the  corpuscles  are  grouped  into 
atoms  or  associated  with  atoms  of  certain  substances,  they 
seem  to  be  able  to  move  then  with  very  much  less  resistance. 

Silver  is  the  best  conductor  known,  and  we  can  imagine 
that  silver  in  some  unknown  way  enables  the  electricity  to 
move  through  the  ether  with  but  very  little  resistance. 

11.  Lines  of  Force. — How  or  why  the  ether  offers  such 
resistance  is  not  known. 

If  a  cardboard  be  placed  around  a  wire,  and  a  current 
of  electricity  be  sent  through  the  wire,  iron  filings  sprinkled 
on  the  cardboard  will  arrange  themselves  in  concentric  circles. 
These  circles  are  called  lines  of  force.  In  .Fig.  62,  let  AB  be 
a  wire  and  let  a  current  pass  through  it  in  the  direction  of 
the  arrow;  then  these  lines  of  force  shown  at  C,  D  and  E  will 
arise  around  the  wire. 

It  is  the  moving  corpuscle  that  sets  them  up.  The  cor- 
puscle, in  a  way  not  knowrn,  being  resisted  by  the  ether,  set- 
up a  strain  or  drag  in  it  in  much  the  same  way  that  a  stone, 
when  thrown  in  the  water,  drags  the  surface  of  the  water  down 
with  it.  As  the  stone  goes  on,  the  surface  bounds  back, 
springing  above  the  surrounding  surface  in  its  backward  mo- 
tion. The  water  then  oscillates  and  waves  are  produced.  Con- 
centric rings  or  waves  are  formed. 

The  corpuscle  in  the  same  manner  forms  concentric  rings 
as  it  plunges  through  the  ether.  The  rings  begin  at  the  cor- 
puscle and  move  outward  perpendicular  to  the  direction  in 
which  the  corpuscle  is  moving. 

By  Ampere's  rule,  the  lines  of  force  circulate  in  the  direc- 
tion of  the  arrows.  If  the  current  be  reversed,  the*  lines  of 
force  flow. in  the  opposite  direction.  If  the  wire  AB-  be  bent 
up  out  of  the  paper  to  form  a  coil,  then  a  north  pole  is  de- 
veloped at  N  and  a  south  pole  at  5.  If  the  wire  was  bent 
down  into  the  paper,  then  the  north  pole  would  be  at  5  and 


126 


WIRELESS  TELEGRAPHY  AND 


the  south  pole  at  Ar,  the  north  pole  always  being  in  the  direc- 
tion in  which  the  lines  of  force  leave  the  inside  of  the  coil 
and  the  south  pole  in  the  direction  from  which  the  lines  of 
force  enter  the  coil. 

On  this  account  two  wires  side  by  side,  carrying  currents 
of  electricity  in  the  same  direction,  attract  one  another,  while 
two  wires  carrying  currents  in  opposite  directions  repel  one 
another.  This  can  readily  be  seen  from  Fig.  63.  If  AB  and 
CD  are  carrying  currents  in  the  same  direction,  then,  at  any 
point  E  where  the  lines  meet,  they  coalesce  and  go  around  both 
wires  as  though  they  were  one  wire,  as  shown  at  E  in  Fig.  64. 


Fig.    63.      Lines   of   force    around   two   wires    carrying   current    in    the 

same  direction. 


Fig.  64.     Lines  of  force  coalesce  around  wires  carrying  current  in  the 
same  direction,  and  hence  attraction  occurs. 


HIGH  FREQUENCY  ELECTRICITY 


127 


Fig.   65.      Lines   of  force   around   wires    carrying   current   in   opposite 
directions,   showing  opposition  and   hence   repulsion. 

But  if  the  current  is  going  in  opposite  directions,  as  in  Fig.  65, 
then  they  cannot  coalesce  and  go  around  both  wires,  as  they 
oppose  one  another.  Hence  the  wires  repel  one  another. 

If  the  current  is  a  direct,  steady  current,  like  that  fur- 
nished by  a  storage  battery,  the  lines  of  force  stand  still  after 
the  current  is  established.  If  the  rate  of  flow  of  the  current 
is  changing,  then  the  lines  move.  If  the  current  is  rising,  the 
lines  of  force  move  outward  away  from  the  wire ;  but  if  the 
current  is  falling,  the  lines  move  toward  the  wire. 

By  experiment  it  is  known  that  these  lines  of  force  set  up 
a  pressure  in  any  wire  that  they  cut.  The  lines  must  be 
moving  in  order  to  set  up  this  pressure.  If  the  ends  of  the 
wire  be  connected  when  it  is  being  cut  by  these  moving  lines 
of  force,  then  a  current  of  electricity  flows  in  the  wire. 

If  the  lines  of  force  stand  still  and  a  conductor  be  moved 
so  as  to  cut'  the  lines  of  force,  perpendicular  to  the  direction 
of  the  wire,  then  a  pressure  is  set  up  in  the  wire,  and,  if  the 
ends  be  connected,  a  current  flows  in  the  -wire. 

Here  again  these  lines  of  force  consist  of  matter  in  motion. 
In  this  case  it  is  a  wave  motion,  however. 

If  iron  filings  be  sprinkled  on  a  piece  of  paper  placed  over 
a  permanent  steel  magnet,  these  lines  of  force  can  also  be  ob- 
served. A  piece  of  steel  becomes  a  magnet  when  its  mole- 
cules are  arranged  regularly  by  stroking  it  with  another  per- 
manent magnet  or  by  passing  a  current  of  electricity  around  it. 


128  '  WIRELESS  TELEGRAPHY  AND 

By  a  simple  series  of  experiments,  this  can  be  shown  to  be 
due  to  an  arrangement  of  the  molecules  of  the  steel.  If  the 
iron  be  soft  and  pure,  the  molecules  will  not  stay  arranged, 
and  then  the  iron  will  be  magnetic  only  when  the  current  is 
flowing  around  it. 

This  latter  is  called  an  electromagnet.  From  this  it  fol- 
lows that  the  molecules  must  be  little  magnets  with  poles,  and, 
if  this  is  the  case,  then  corpuscles  of  electricity  must  be  cir- 
culating around  the  molecules  in  the  same  direction  in  order 
to  produce  poles  in  them. 

If  wires  are  moved  so  as  to  cut  these  lines  of  force  per- 
pendicularly, then  pressures  will  be  set  up  in  the  wires.  Mag- 
nets develop  two  poles,  a  north  and  a  south  pole,  and  it  is 
well  known  that  like  poles  repel  one  another  while  unlike 
poles  attract  one  another. 

The  lines  of  force,  however,  repel  one  another.  If  they 
are  flowing  in  the  same  direction,  then  they  coalesce  into 
one  line  and  their  sources  are  attracted,  but  if  they  are  flowing 
in  opposite  directions,  they  will  not  coalesce  and  their  sources 
repel  one  another. 

In  Fig.  66,  for  example,  the  lines  flow  from  the  north  pole 
through  the  air  to  the  south  pole  and  back  to  the  north  pole 
from  the  south  pole  through  the  iron.  If  two  poles  be  ap- 
proached, they  will  either  repel  one  another  or  attract  one 
another. 

If  a  north  and  a  south  pole  be  approached  as  in  Fig.  65, 
the  lines  of  force  at  E  coalesce,  since  they  are  running  in  the 
same  direction  as  they  meet ;  but  if  two  south  poles  be  brought 
together,  as  in  Fig.  6j,  the  lines  of  force  are  running  in  op- 
posite directions  when  they  meet,  and  hence  they  oppose  one 
another  and  repel. 

12.  Amperes. — The  rate  of  flow  of  the  current  is  called 
its  amperage.  It  is  usually  represented  by  /.  A  current  of 
electricity  from  a  storage  battery  is  called  a  steady  direct 
current,  because  it  has  an  even  continuous  rate  of  flow.  A 
current  of  electricity  from  a  dynamo  is  an  intermittent  direct 
current  because  the  rate  of  flow  is  not  always  the  same.  If 
the  dynamo  has  a  frequency  of  60  cycles  per  second,  the 


HIGH  FREQUENCY  ELECTRICITY 


129 


current  rises  from  zero  to  a  maximum  and  falls  from  a  maxi- 
mum to  zero.  120  times  per  second,  but  always  in  the  same 
direction. 

The  direct  current  of  a  dynamo  is  a  rectified  alternating 
current.  The  current  is  rectified  by  the  comutator.  If  slip 
rings  are  used  instead  of  a  comutator,  then  the  current  will  be 
alternating.  If  the  machine  has  a-  frequency  of  60  cycles, 
there  will  be  120  alternations  per  second,  and  the  current  will 
rush  first  one  way  through  the  wire  with  great  rapidity  and 
then  back  again. 


Fig.  66.    Diagram  showing  lines  of  force  around  north  and  south  poles 
of  a  magnet.     Lines  coalesce,  and  hence  magnets  attract. 


Fig.  67.     Diagram  of  lines  of  force  around  two  north  poles,  showing 
opposition  and  repulsion. 


Fig.  68.     Diagram  of  instantaneous  values  of  current  and  voltage  in 

an    alternator. 

13.     The  Alternator. — Let  Fig.  68  represent  an  alternator, 
in  which  N  and  5*  are  the  north  and  south  poles  of  the  field. 


130  WIRELESS  TELEGRAPHY  AND 

Let  ABC  be  an  armature  revolving  between  the  poles.  Let 
the  little  circles  represent  cross  sections  of  wires  cutting  across 
the  lines  of  force. 

If  the  armature  be  rotating  in  the  direction  of  the  arrow, 
the  value  of  the  current  and  pressure  at  A  is  zero,  and  at  / 
it  is  a  little  greater,  at  2  a  little  larger  still,  and  at  j  still 
greater,  while  a  little  beyond  4  it  is  at  a  maximum.  In  the 
same  manner  it  falls  to  zero  on  the  other  side.  The  current 
reverses  at  C  and  rises  from  zero  to  a  maximum  in  the  oppo- 
site direction. 

If  we  lay  out  a  line  AFM  equal  in  length  to  the  circle 
and  divide  it  into  degrees,  there  will  be  360  degrees  in  this 
line,  180  at  F,  one-half  of  the  line ;  90  degrees  at  0,  one- 
quarter  of  the  line ;  and  270  degrees  at  P,  three-quarters  -of 
the  line.  Through  the  wires  I,  2,  j,  4,  draw  lines  parallel  to 
the  line  AFM.  Lay  off  the  points  20,  40,  60  and  80,  20  degrees 
apart  on  the  line  AF.  Erect  perpendiculars  at  these  points  to 
the  line  AF.  The  points  in  which  the  parallel  lines  from 
i,  2,  3,  4?  and  the  perpendicular  lines  20,  40,  60  and  80  cut  each 
other  respectively,  represent  the  instantaneous  value  of-  the 
pressure  and  current  developed  in  the  wire  at  that  point,  by 
its  rate  of  cutting  the  lines  of  force. 

14.  Sine  Curve. — Draw  a  smooth  curve  connecting  these 
points.     Construct  the  balance  of  the  curve  in  the  same  man- 
ner.   This  curve  represents  the  rise  and  fall  of  the  alternating 
current  and   its   reversal   in   one   revolution   of  the   armature. 
This  is  called  a  sine  curve. 

From  this  it  can  be  seen  that  the  current  has  not  the 
same  value  all  of  the  time  in  the  circuit,  because  at  A  the  wrire 
is  running  parallel 'to  the  lines  of  force  and  the  pressure  and 
current  are  zero.  As  it  rotates  it  cuts  across  the  lines,  hence 
at  i  it  is  greater  than  at  A.  At  4  it  is  cutting  the  lines 
perpendicularly  and  here  it  has  its  greatest  value,  etc. 

15.  Rectified  Curve. — If  this  current  be  rectified,  then  the 
curve  is  like  Fig.  6p.     The  lower  part  of  the  curve  of  Fig.  69 
is  then  in  the  same  direction  as  the  upper  part  of  the  curve, 
but  the  current  rises  and  falls  with  the  same  frequency.    Hence 
the   corpuscles   are   not  at   the   same   density   throughout   the 


HIGH  FREQUENCY  ELECTRICITY  131 


ABC 

Fig.   69.      Rectified    sine    wave. 

wire.    The  alternating  current  is  used  largely  in  wireless  teleg- 
raphy, while  the  direct  is  used  in  wireless  telephony. 

16.  Origin    of    Pressure    or    Voltage. — When    the    con- 
ductors in  Fig.  68  are  rotated  across  the  lines  of  force,  these 
lines  resist  the  motion,  due  to  the  fact  that  the  lines  resist 
the  motion  of  the  corpuscles  of  which  the  atoms  of  wire  are 
composed.     The   lines   then   drag   the   corpuscles   loose   from 
the  atoms  and  press  them  along  in  the  conductor. 

As  they  are  continually  pressing  these  corpuscles  along, 
by  dragging  more  of  them  loose  and  pressing  them  along,  it  is 
the  motion  of  the  wire  across  the  lines  of  force  that  produces 
the  pressure  or  voltage  of  the  machine. 

The  rate  of  flow  of  the  corpuscles  under  this  pressure  is 
the  amperage  of  the  current,  and  the  resistance  that  the  wires 
offer  to  the  moving  corpuscles  is  the  resistance. 

In  the  alternating  current  there  are  other  resistances  be- 
sides that  due  to  the  ohmic  resistance  of  the  wire.  Every  al- 
ternating circuit  has  what  is  known  as  capacity  and  induct- 
ance. 

In  order  to  understand  inductance,  it  is  necessary  to  know 
something  about  what  is  known  as  inertia  of  matter. 

17.  Inertia. — Inertia  is  a  property  of  all  matter  so  far  as 
we  know.    By  inertia  is  meant  that  property  of  matter  where- 
by it  tends  or  persists  in  remaining  in  a  condition  of  rest  or 
motion.     By  virtue  of  this  property,  all  matter  resists  being 
disturbed,  and  when  once  disturbed  it  persists  in  remaining 
in  its  new  state. 

To  illustrate :  A-  heavy  wagon  resting  on  a  smooth  road 
requires  the  expenditure  of  considerable  energy  to  start  it, 


132  WIRELESS  TELEGRAPHY  AND 

but  when  started  it  can  be  kept  moving  easily.  The  question 
of  weight  is  eliminated  here.  It  is  the  mass  of  the  wagon  that 
^we  have  to  deal  with  and  that  mass  resists  being  moved.  The 
larger  the  mass,  the  more  force  it  will  require  to  start  it. 
After  it  is  once  started,  it  does  not  require  much  force  to 
keep  it  moving.  When  once  moving  it  requires  as  much  force 
to  stop  it  as  was  exerted  to  start  it. 

The  cause  of  inertia  is  not  known,  but  it  may  be  due  to 
the  resistance  that  the  ether  offers  to  a  change  of  state  in 
matter.  That  is,  the  ether  offers  resistance  to  any  change  in 
rate  of  motion  or  a  change  from  a  state  of  rest  to  a  state  of 
motion. 

The  lines  of  force  or  the.  strains  set  up  in  the  ether  by 
the  corpuscles  are  due  to  the  resistance  which  the  ether  of- 
fers to  the  motion  of  the  corpuscles  through  it,  and  it  is  this 
resistance  which  constitutes  the  inertia  of  the  electric  current. 
It  is  only  when  the  current  is  increasing  or  decreasing  that 
this  resistance  is  manifested. 

18.  Inductance. — This  resistance  is  called  inductance, 
and  it  is  a  constant.  It  is  defined  as  that  coefficient  by  which 
the  time  rate  of  change  of  the  current  must  be  multiplied 
in  order  to  produce  the  back  electromotive  force  of  self  in- 
duction. A  steady  direct  current  has  no  inductance.  Induct- 
ance is  present  only  when  lines  of  force  are  rising  or  falling. 

If  CDB  is  the  cross  section  of  a  wire  in  Fig.  70,  and  the 
concentric  circles  represent  lines  of  force,  due  to  a  single  cor- 
puscle in  the  center  of  the  wire,  then  these  lines  of  force  cut 
the  wire  DEC  itself,  and  in  doing  so  set  up  a  pressure  and  a 
current  in  opposition  to  the  corpuscle.  This  back  pressure 
is  known  as  the  electromotive  force  of  self  induction. 

If  A  is  a.  second  wire  near  the  wire  DEC,  then  the  lines  of 
force,  due  to  a  current  moving  down  into  the  page,  rise  out  and 
cut  the  wire  A.  When  they  do  this,  they  tear  loose  corpuscles 
in  A  and  set  them  to  flowing  up  from  the  paper  in  the  oppo- 
site direction  to  those  in  the  first  wire. 

This  is  known  as  induction  and  the  interaction  between 
these  wires  due  to  the  current,  induced  in  A,  setting  up  lines 
of  force,  swelling  out  from  A,  is  known  as  mutual  induction. 


HIGH  FREQUENCY  ELECTRICITY 


133 


Fig.  70 

These  wires  will  then  repel  one  another  and  their  fields  will 
oppose  one  another.  If  CDB  has  a  current  in  it  distributed, 
evenly  throughout  its  cross  section,  then  each  corpuscle  sets 
up  lines  of  force. 

Since  these  corpuscles  are  all  moving  in  the  same  direc- 
tion, they  attract  one  another  and  their  lines  of  force  coalesce 
more  or  less,  as  shown  in  Figs.  63  and  64.  They  thus  assist 
one  another,  and  their  combined  lines  of  force,  in  cutting  the 
wire  CDB,  set  up  in  it  a  back  pressure  parallel  to  the  back 
pressure  in  A  and  in  the  same  direction.  This  back  pressure 
is  called  the  electromotive  force  of  self  induction.  The  in- 
ductance of  the  \vire  is  denoted  by  L.  This  L  is  a  constant 
in  any  given  fixed  circuit,  but  the  back  pressure  or  E.M.F.  of 
self  induction  depends  upon  the  time  rate  of  change  of  the  cur- 


134 


WIRELESS  TELEGRAPHY  AND 


rent.     If  the  current  is  changing  rapidly,  the  back  E.M.F.  is 
stronger. 

By  referring  to  Fig.  68,  it  will  be  seen  that  the  value  of 
the  current  and  pressure  is  changing  rapidly  at  A.  The 
current  and  pressure  are  zero  here  and  as  the  wire  rotates 
the  value  changes  very  quickly  from  zero  to  some  value.  As 
the  wire  rotates  to  position  2,  there  is  a  rapid  change  in  the 
value  of  the  current,  but  less  of  a  change  than  took  place  in  its 
movement  from  zero  to  /.  In  moving  from  j  to  4,  the  current 
has  just  about  reached  its  full  value  and  hence  the  change  in 
the  value  of  the  current  is  small.  Hence  the  inductance  is 
great  at  A  and  small  at  4,  while  the  current  is  small  at  i  and 
the  E.M.F.  of  self  induction  is  large.  From  this  it  is  easily  seen 


Fig.  71.     Lines  of  strain  around  a  condenser. 

that  the  inductance  and  the  current  of  the  dynamo  are  90 
degrees  apart,  for  when  one  is  zero,  the  other  is  at  a  maximum. 
The  inductance  thus  leads  the  current  by  90  degrees. 

19.  Capacity. — If  two  conducting  plates  be  put  near  one 
another  in  air  and  each  one  is  connected  to  a  battery  as  shown 
in  Fig.  //,  the  plates  become  charged  with  electricity,  and  lines 


HIGH  FREQUENCY  ELECTRICITY 


135 


of  force  or  strains  are  set  up  in  the  ether.  If  A  and  B  are 
two  metal  plates  and  C  is  a  battery,  lines  of  force  spring  across 
from  A  to  B  between  the  plates,  and  they  also  proceed  from 
A  to  B  through  the  air  around  the  ends  of  A  and  B  as  shown 
in  the  figure. 

The  air  is  an  insulator  and  it  is  called  a  dielectric.  The 
corpuscles  are  vibrating  back  and  forth  over  the  surface  of 
the  plates  or  in  the  air  next  to  the  plates  and  these  lines  of 
strain  are  set  up.  As  the  capacity  is  charged,  the  lines  of 
force  rise,  and  when  it  is  discharged  they  fall  towards  the 
plates.  These  may  be  called  electrostatic  lines  of  force  to 
distinguish  them  from  the  electromagnetic  lines  of  force,  and 
the  space  about  the  capacity  is  called  an  electrostatic  field 
of  force. 

When  a  capacity  is  put  in  series  with  a  source  of  alter- 
nating current,  the  current  surges  into  and  out  of  the  capacity 
as  it  alternates,  and  thus  the  current  practically  flows  through 
the  capacity,  although  it  does  not  actually  go  through  the 
dielectric.  A  very  weak  current,  however,  penetrates  the  di- 
electric, because  no  dielectric  is  a  perfect  insulator.  The 
higher  the  voltage  of  the  charging  current,  the  more  the  cur- 
rent goes  through,  and  in  case  of  high  voltages  the  leak 
through  the  dielectric  may  be  considerable. 

When  a  capacity  is  charged  by  the  direct  current,  the  pres- 
sure of  the  charging  current  is  at  a  maximum  when  the  charg- 


Fig.  72.     Action  of  an  alternator  with  an  inductive  and  capacity  load. 


136  WIRELESS  TELEGRAPHY  AND 

ing  begins,  and  the  back  pressure  of  the  capacity  is  then  zero. 
As  the  capacity  charges,  its  back  pressure  rises  until  it  is 
equal  to  that  of  the  charging  current. 

20.  Capacity  Reaction. — When  the  alternating  current  is 
charging  a  capacity,  the  action  is  somewhat  different.  In 
Fig.  72,  let  S  and  V  be  two  slip  rings  upon  which  the  coil  5 
terminates.  Let  lines  of  force  stream  across  from  N  to  S,  N 
and  5  being  the  north  and  south  pole  of  the  field  of  an  alter- 
nator. Let  B  and  E  be  brushes  connecting  the  slip  rings  to 
an  external  circuit,  containing  the  capacity  C  and  the  induct- 
ance L.  When  the  coil  C  is  at  i,  the  pressure,  current  and 
inductance  pressure  of  the  machine  are  all  zero. 

As  the  coil  moves  from  I  to  <?,  the  current  begins  to  flow, 
but  it  is  weak.  Its  rate  of  change  is  large,  however,  and 
hence  the  inductance  pressure  is  large,  since  its  value  depends 
upon  the  rate  of  change  of  current.  The  pressure  of  the  ma- 
chine is  small.  The  condenser  begins  to  charge. 

As  the  coil  rotates  to  90  degrees,  the  current  and  voltage 
of  the  machine  rise  to  a  maximum,  but  since  the  back  pressure 
of  the  capacity  also  rises,  the  current,  after  the  coil  has  ro- 
tated a  certain  distance,  reaches  its  highest  value  before  reach- 
ing 90  degrees.  This  -highest  value  is  reached  when  the  back 
pressure  of  the  condenser  reaches  a  value  such  as  to  oppose 
any  increase  in  the  current  due  to  the  pressure  of  the  ma- 
chine. 

After  the  current  reaches  a  maximum,  it  begins  to  decline. 
The  pressure  of  the  machine  rises  and  also  the  opposing  pres- 
sure of  the  capacity  rises,  the  current  decreasing  all  of  the 
time,  until  90  degrees  is  reached,  where  the  pressure  of  the 
machine  and  capacity  are  at  a  maximum.  The  pressure  of  the 
capacity  here  is  exactly  equal  to  the  pressure  of  the  alter- 
nator and  the,  current  of  the  alternator  is  zero. 

The  inductance  pressure  also  rose  and  fell  with  the  rate 
of  change  of  the  current.  Between  i  and  2  the  inductance 
pressure  was  large,  and  it  opposed  the  pressure  of  the  alter- 
nator and  acted  with  the  pressure  of  the  capacity.  When  the 
current  reached  a  maximum,  the  inductance  pressure  became 
zero.  As  the  current  declined  in  value  with  the  rotation  of 


HIGH  FREQUENCY  ELECTRICITY  137 

the  coil  toward  90  degrees,  the  pressure  of  the  inductance 
again  appeared,  its  value  depending  upon  the  rate  of  decay 
of  the  current,  but  in  this  case  this  pressure  is  reversed  and 
it  is  exerted  against  the  pressure  of  the  capacity  and  with 
the  pressure  of  the  charging  current. 

The  current  ceases  to  flow  at  90  degrees,  since  the  ca- 
pacity pressure  and  the  pressure  of  the  alternator  are  just 
equal,  and  the  inductance  pressure  at  this  point  is  zero. 

If  an  inductance  L  be  placed  in  the  external  circuit,  it  can 
be  adjusted  so  that  its  pressure  offsets*  the  value  of  the  ca- 
pacity back  pressure  on  the  decaying  charging  current,  because 
the  pressure  due  to  the  inductance  assists  the  pressure  of  the 
machine.  This  prevents  the  capacity  from  charging  on  the 
rising  current  and  allows  it  to  charge  strongly  on  the  falling 
current.  When  this  is  done,  resonance  is  secured. 

From  4  to  7  the  pressure  of  the  alternator  falls  and  the 
condenser  begins  to  discharge.  Its  rate  of  change  of  dis- 
charge is  high  at  first  and  hence  the  back  pressure  of  in- 
ductance of  the  discharge  current  is  large.  Hence  the  back 
E.M.F.  of  inductance  from  4  to  5  is  large.  The  charging  of 
the  condenser  is  in  the  direction  of  the  arrows.  But  the  con- 
denser discharge  is  in  the  reverse  direction. 

The  pressure  of  the  machine  is  also  large,  and  this  pres- 
sure and  the  back  pressure  of  inductance  check  the  discharge 
of  the  condenser.  As  the  coil  approaches  /,  the  pressure  of 
the  machine  drops  rapidly.  The  current  discharge  reaches  a 
maximum  somewhere  between  4  and  /,  when  the  pressure  from 
the  condenser  has  such  a  value  as  to  prevent  the  pressure  of 
the  alternator  and  its  inductance  pressure  from  increasing 
the  current.  Then  the  discharge  current  of  the  condenser  be- 
gins to  decline.  Hence  the  inductance  pressure  again  rises, 
but  this  time  acting  with  the  pressure  of  the  capacity  and 
against  that  of  the  alternator.  The  exterior  inductance  L  also 
acts  in  the  same  manner. 

But  here  the  discharge  current  is  rushing  into  the  other 
side  of  the  condenser,  and  this  inductance  L  is  just  great 
enough  to  offset  the  back  pressure  of  the  other  side  of  the 
now  charging  condenser,  and  hence  the  condenser  charges 
freely. 


138  WIRELESS  TELEGRAPHY  AND 

As  7  is  reached  the  current  from  the  machine  is  set  up  in 
the  direction  opposite  to  the  arrows  and  assists  the  capacity 
discharge  into  its  other  side. 

21.  Resonance. — The  same  operation  takes  place  from  7 
to  12,  but  in  the  reverse  direction.     The  current  thus  flows 
from  one  side  of  the  condenser  to  the  other,  back  and  forth 
through  the  machine,  and  if  the  capacity  and  inductance  L 
are   adjusted   to  the  right  values   so  that  the   pressure  of  L 
can  just  overcome  the  capacity  pressure  when  acting  against 
it,  resonance  is  secured  and  a  maximum  result  is  obtained. 

It  is  thus  seen  that  at  the  beginning  of  charge  and  dis- 
charge, the  current  is  checked  by  the  inductance  pressure  until 
the  current  reaches  a  maximum,  but  at  the  maximum  the 
inductance  pressure,  due  to  a  falling  current,  assists  the  charg- 
ing pressure  and  the  capacity  charges  rapidly  and  freely,  pro- 
vided the  value  of  the  inductance  pressure  is  adjusted  to  the 
right  amount.  If  the  inductance  pressure  of  L  is  too  large, 
its  value  is  such  as  to  destroy  the  pressure  of  the  alternator 
and  hence  the  current  cannot  be  built  up  to  a  sufficient  value 
to  charge  the  capacity. 

A  capacity  large  enough  to  load  the  machine  properly  for 
the  work  in  hand  is  used.  Then  the  inductance  is  adjusted 
until  a  resonance  value  is  secured  as  detailed  above. 

22.  Condenser. — The   term   capacity   is   a   term    used   to 
designate  a  fixed  quality  of  a  condenser  due  to  the  size  of  the 
condenser  plates,  their  distance  apart  and  the  dielectric  con- 
stant of  -the  insulating  material.    A  condenser  is  a  contrivance 
for  holding  electricity,  the  same  as  a  glass  is  a  contrivance 
for  holding  water.    The  condenser  is  made  of  two  conducting 
plates  placed  parallel  to  one  another  and  separated  by  an  in- 
sulating material.     The  insulating  material  may  be  air,  glass, 
oil,  etc. 

When  a  condenser  is  charged  as  in  Fig.  71,  electrostatic 
lines  of  force  spring  across  from  plate  to  plate.  The  number 
of  these  lines  per  square  inch  or  per  square  centimeter  depends 
upon  the  voltage  of  the  charging  current,  the  distance  of  the 
plates  apart  and  the  nature  of  the  insulating  substance. 

The   insulating  substance   is   called   a   dielectric,   and  the 


HIGH  FREQUENCY  ELECTRICITY  139 

quality  of  the  dielectric  whereby  it  conducts  electrostatic  lines 
of  force  is  called  its.  dielectric  constant.  Different  dielectrics 
conduct  electrostatic  lines  of  force  differently.  If  air  is  taken 
as  unity,  then  glass  will  conduct  the  electrostatic  lines  of  force 
from  six  to  nine  times  as  easily  as  air.  The  oils  generally 
have  a  dielectric  constant  of  two  times  that  of  air. 

Pure  water  has  eighty  times  and  glycerine  fifty-six  times 
the  conductivity  of  air.  Electrostatic  and  electromagnetic 
lines  of  force  are  both  strains  in  the  ether  due  to  the  corpuscle 
of  electricity,  but  they  are  also  different  because  glass  has  no 
effect  upon  electromagnetic  lines  of  force,  while  it  has  a  great 
effect  upon  electrostatic  lines  of  force.  The  metal  plates  of  a 
condenser  act  only  as  conductors  of  the  current,  and  the  charge 
resides  in  the  dielectric. 

The  capacity  of  a  condenser  then  depends  upon ;  first,  the. 
dielectric  constant  or  inductivity  of  the  insulating  material ; 
second,  the  area  of  the  conducting  plates ;  and  third,  their 
distance  apart.  The  farther  the  plates  are  apart  the  thicker 
the  dielectric  and  the  greater  its  resistance  to  the  flow  of  the 
lines  of  force;  consequently,  less  current  will  flow  into  the 
condenser  under  a  given  pressure. 

The  quantity  of  electricity  that  a  condenser  will  hold 
depends  upon  its  capacity  and  the  charging  voltage.  The  am- 
pere designates  the  rate  of  flow  of  the  current,  the  same  as 
two  quarts  per  second  might  designate  the  rate  of  flow  of  the 
water  in  a  pipe,  but  neither  one  of  these  give  us  the  quantity 
of  electricity  or  water  that  has  flowed.  In  order  to  get  the 
quantity  that  has  passed,  it  is 'necessary  to  multiply  by  the 
time  it  has  been  flowing. 

Thus,  2  quarts  of  water  per  second  flowing  in  a  pipe  in 
10  seconds,  gives  10  times  2  quarts,  or  20  quarts,  as  the 
quantity  of  water  that  can  be  caught  in  a  pail  in  that  time. 

In  the  same  manner  the  amperes  or  rate  of  flow  of  the 
electric  current,  multiplied  by  the  time  it  is  flowing,  gives  the 
quantity  of  electricity  that  can  be  caught  in  a  condenser. 

For  instance,  a  rate  of  flow  of  2  amperes  per  second  for 
10  seconds  gives  20  coulombs  of  electricity.  The  coulomb  is 
the  name  for  the  quantity  of  electricity  the  same  as  the  quart 


140 


WIRELESS  TELEGRAPHY  AND 


is  for  water.  If  Q  stands  for  coulombs,  /  for  amperes,  t  for 
time  in  seconds,  and  E  for  voltage  or  pressure,  then  It=Q  = 
CE,  where  C  is  the  capacity  of  the  condenser,  in  farads. 

In  order  to  make  the  matter  clear,  see  Fig.  73.  Let  D  be 
a  glass  dish,  with  a  spout  A  connecting  with  a  funnel  BC. 
Suppose  the  spout  A  to  be  filled  with  a  resisting  substance, 
like  sand  for  instance,  that  obstructs  the  free  flow  of  the  water. 


C 


Fig.  73 

Let  the  area  of  the  bottom  of  the  dish  D,  and  the  resistance 
in  A  be  called  the  capacity  of  D  for  holding  water.  It  is  easily 
seen  that  -this  capacity  does  not  mean  the  quantity  of  water 
that  D  can  hold.  In  order  to  obtain  the  quantity  of  water  D 
can  hold,  it  is  necessary  to  know  the  depth  of  the  dish  A.  In 
order  to  know  the  quantity  of  water  D  will  hold  under  any 
given  pressure  in  BC,  it  is  necessary  to  know  the  cross  section 
of  D,  the  resistance  in  A  and  the  depth  or  pressure  of  the 
water  in  BC.  If  there  is  much  resistance  in  A,  the  water  will 
not  rise  in  D  as  high  as  it  stands  in  BC. 

In  this  figure  the  area  of  the  bottom  of  D  and  the  resist- 
ance in  A  represent  the  capacity  of  the  condenser.  The  re- 
sistance in  A  represents  the  resistance  that  the  dielectric  offers 
to  the  flow  of  the  lines  of  force. 

If  BC  be  filled  with  water,  the  pressure  exerted  by  the 
weight  of  the  water  -will  cause  it  to  flow  over  into  the  dish 
D,  and  if  there  is  no  resistance  in  A,  the  water  will  flow  into 
D  until  it  is  at  the  same  height  in  both  BC  and  D  ;  but  if 


HIGH  FREQUENCY  ELECTRICITY  141 

there  is  a  resistance  in  A,  then  it  will  exert  a  back  pressure, 
and  the  water  will  not  rise  as  high  in  D  as  it  remains  in  BC. 

If  the  spout  A  is  increased  in  length,  its  resistance  in- 
creases correspondingly,  and  the  height  to  which  the  water 
will  reach  in  D  is  proportionately  less.  In  a  condenser  the 
same  thing  takes  place.  The  pressure  of  the  charging  machine 
forces  the  current  into  the  condenser  until  the  back  pressure 
of  the  condenser  equals  the  charging  pressure.  The  area  of  the 
plates  and  the  resistance  of  the  dielectric  to  the  flow  of  the 
lines  of  force  determine  the  quantity  of  electricity  that  will 
flow  into  the  condenser,  before  its  back  pressure  becomes 
equal  to  the  charging  pressure. 

It  is  seen  that  the  depth  of  the  water  represents  the  pres- 
sure or  voltage  of  the  current.  If  the  depth  be  increased,  then 
the  quantity  of  water  in  the  dish  is  increased.  In  the  con- 
denser, if  the  pressure  is  increased,  the  quantity  of  electricity 
in  the  condenser  is  increased.  Since  the  electrostatic  lines  of 
force  flow  more  easily  through  glass  than  air,  a  greater  quan- 
tity of  electricity  will  flow  into  a  condenser  having  a  glass 
plate  for  a  dielectric  instead  of  air,  because  the  lines  of  force 
do  not  press  back  as  much  when  glass  is  used. 

The  thing  to  be  held  in  mind  is  that  the  capacity  of  a 
given  condenser  is  a  fixed  quantity  and  that  the  amount^ of 
electricity  a  condenser  will  hold  depends  upon  the  voltage  of 
the  charging  current.  In  Fig.  73,  if  the  height  of  the  water  in 
BC  is  increased,  the  height  of  the  water  in  D  will  be  increased, 
although  the  capacity  of  D  remains  the  same. 

If  the  height  of  the  wrater  in  BC  increases  until  it  is  higher 
than  the  rim  of  'D,  then  the  water  will  overflow  and  D  cannot 
be  made  to  hold  any  more  water.  Also,  if  the  pressure  of  a 
charging  current  be  raised  in  a  condenser,  a  point  will*  be 
reached  where  the  condenser  will  hold  no  more  and  the  con- 
denser will  leak,  sending  out  into  the  air  a  fine  electric  spray. 

Suppose  D  and  BC  to  be  very  high  or  deep.  Then  if 
water  be  poured  into  BC,  a  point  will  be  reached  where  the 
glass  can  no  longer  stand  the  pressure  and  the  glass  will 
break. 

If  a  condenser  be  put  in  oil  so  that  it  cannot  leak,  and 


142 


WIRELESS  TELEGRAPHY  AND 


if  the  voltage  of  the  charging  current  be  increased,  a  point 
will  be  reached  where  the  glass  can  no  longer  stand  the  strain 
and  the  glass  will  break.  The  electricity  resides  in  the  di- 
electric and  as  the  pressure  increases,  it  soaks  deeper  and 
deeper  into  the  dielectric,  and  when  the  pressure  becomes 
great  enough,  it  punctures  the  dielectric. 

23.  The    Transformer. — The    transformer    or    induction 
coil  is  an  electric  machine  for  the   purpose  of  transforming 
electric  currents  from  one  amperage  and  voltage  to  another 
amperage  and  voltage.     When  the  voltage  is  stepped  up,  the 
amperage  is  stepped  down  in  the  same  ratio,  and  when  the 
voltage  is  stepped  down,  the  amperage  is  stepped  up  in  the 
same  ratio.     The  former  is  called  a  step-up  transformer,  and 
the  latter  is  called  a  step-down  transformer.    The  transformer 
is  used  on  the  alternating  current  and  the  induction  coil  on  the 
direct  current. 

Transformers  can  be  conveniently  divided  into  three 
classes,  viz. :  Air  core  or  Tesla  transformers ;  open  iron  core 
transformers,  and  closed  iron  core  transformers. 

24.  The  Induction  Coil. — The  induction  coil  is  an  open 
iron  core  transformer,  in  which  the  lines  of  force  are  caused 
to  rise  and  fall  by  means  of  a  vibrator. 


Fig.   74.     Diagram  of  an  induction   coil. 

Fig.  74  gives  the  connection  to  the  vibrator.  Many  ex- 
cellent works  have  been  written  on  the  construction  and  op- 
eration of  induction  coils,  and  the  reader  is  referred  to  them 


HIGH  FREQUENCY  ELECTRICITY 


143 


for  further  information.  Any  of  the  transformer  designs  in 
this  book  can  be  altered  to  induction  coils  by  using  only  one 
leg  of  the  transformer.  Wind  the  primary  as  directed  in  Fig.  4, 
insulate  heavily  with  empire  cloth  and  assemble  the  secondary 
over  the  primary.  For  wireless  the  core  of  the  induction  coil 
should  be  rather  short  and  thick.  The  secondary  should  be 
wound  in  pies  as  directed  in  Fig.  5. 

When  constructed  thus  it  is  an  open  iron  core  trans- 
former, that  can  be  used  the  same  as  the  other  transformers, 
but  it  is  very  inefficient  in  its  operation. 

If  a  vibrator  or  Wehnelt  interrupter  is  used  and  the  di- 
rect current  instead  of  the  alternating,  we  have  the  in- 
duction coil.  As  the  circuit  is  closed,  the  current  builds  up 
slowly  and,  consequently,  the  lines  of  force  rise  slowly.  When 
these  lines  cut  the  secondary  wires,  they  induce  in  them  a 
current  in  the  opposite  direction,  and  these  currents  also  set 
up  lines  of  force  which  oppose  those  in  the  primary,  as  ex- 
plained in  Fig.  65.  When  the  primary  current  is  broken,  how- 
ever, the  lines  of  force  fall  very  rapidly,  and,  as  they  fall,  they 
cut  the  secondary  wires,  setting  up  a  current  and  pressure  in 
the  same  direction  as  in  the  primary. 

N  l 


I  V  V 


n 


X*N  f\ 


J  J  J 

\J  \^S  \^ 


Fig.  75.     Diagram  of  a  transformer. 
E,  alternator;    M,  primary;   X,  secondary;  APCS,  closed  iron  circuit. 


144 


WIRELESS  TELEGRAPHY  AND 


On  account  of  the  rapidity  with  which  the  lines  cut  the 
secondary  wires,  the  voltage  developed  in  the  secondary  is 
very  high.  The  induction  coil  is  a  very  inefficient  transformer 
of  energy  and  the  vibrators  are  exceedingly  troublesome,  but 
where  the  alternating  current  cannot  be  obtained,  its  use  is 
necessary. 

25.  Closed  Iron  Core. — The  closed  iron  core  transformer 
is  shown  in  Fig.  75.  M  is  the  primary  connected  to  the  alter- 
nator E.  N  is  the  secondary  and  APCS  is  the  iron  core  made 
up  of  laminated  transformer  iron. 

N 


Fig.   76. 


Action   of  lines   of  force   in   a 
iron  circuit. 


transformer   with    closed 


E,  alternator;  M,  primary;  N,  secondary;  D,  F,  F,  lines  of  force 
swelling  out  from  primary;  H,  final  path  of  lines  of  force  in  iron; 
L,  leakage  lines  of  force  due  to  lines  of  force  at  K. 

In  Fig.  f6  let  E  be  an  alternator  and  let  the  current  at 
any  instant  in  the  primary  M  be  in  the  direction  of  the  arrows. 
Then  according  to  the  right-hand  rule  the  lines  of  force  that 
rise  from  the  primary  wire  at  D  will  flow  in  the  direction  as 


HIGH  FREQUENCY  ELECTRICITY  145 

indicated  by  the  arrows  at  F  and  K.  These  lines  of  force 
form  circles  about  the  wire.  The  portions  of  the  circles  at  H, 
near  the  iron,  fall  immediately  into  the  iron  leg  SC.  The  por- 
tion of  the  circles  designated  F,  swell  outward  from  the  wire 
and  cannot  reach  the  leg  SC.  Since  the  leg  AP  offers  a  path 
to  these  lines  of  force,  they  immediately  collapse  into  the  leg 
AP  and  then  the  line  of  force  circulates  around  through  the 
iron  core  in  the  direction  of  arrows,  as  shown  at  H.  As  these 
line.s  of  force  cut  the  secondary  TV,  they  set  up  a  pressure  and 
current  in  it  in  the  opposite  direction  to  the  current  in  the 
primary  M,  as  can  be  seen  by  applying  the  right-hand  rule. 
Iron  is  an  excellent  conductor  of  the  lines  of  force  and 
the  air  compared  with  iron  is  a  very  poor  conductor  of  these 
lines.  If  the  ends  AS  and  CP  were  removed,  the  air  gap  at 
these  points  would  offer  great  resistance  to  the  passage  of  the 
lines  and,  consequently,  many  of  the  lines  would  rise  up  in 
the  air,  as  shown  at  K,  and  circulate  entirely  through  the  air 
and  the  leg  SC,  as  shown  at  L  in  the  figure.  The  line  L 
would  not  cut  the  secondary  at  all,  and  its  energy  would  not 
be  transformed.  If  the  iron  ends  PC  and  AC  are  present,  the 
line  of  force  shown  at  K,  instead  of  swelling  out  and  following 
the  path  L  through  the  air,  roll  over  and  fall  into  the  leg  AP, 
thus  being  compelled  to  cut  the  secondary.  It  does  this  be- 
cause it  finds  less  resistance  to  its  flow  through  AP  than  it 
does  through  the  air  along  L. 

Not  very  much  is  to  be  gained  by  winding  the  primary  on 
both  legs  and  then  putting  the  secondaries  over  the  primaries. 
The  difficulties  of  insulation  are  very  much .  greater.  The 
length  of  the  leg  AS  and  PC  must  be  greater  in  order  to 
separate  the  coils  on  each  leg  more  fully.  It  requires  much 
more  wire  in  the  secondary  for  the  same  voltage  and  this  adds 
to  the  resistance  of  the  secondary,  which  is  a  very  important 
factor  in  wireless.  For  these  reasons  it  is  better  to  wind  the 
primary  on  one  leg  and  the  secondary  on  the  other  leg. 

Small  commercial  transformers  range  in  efficiency  from 
90%  to  95%,  and  large  ones  reach  an  efficiency  of  98%  to 
99%.  This  is  the  case  only  when  the  resistance  of  the  second- 
ary is  low.  The  resistance  of  the  secondary  in  high  potential 


146  WIRELESS  TELEGRAPHY  AND 

transformers  is  large,  and  their  efficiency  falls  as  low  as  80% 
to  85%. 

If  poor  transformer  iron  is  used,  the  efficiency  falls  as 
low  as  50%,  and  in  induction  coils  and  open  core  transform- 
ers it  falls  very  much  lower.  If  the  transformer  is  put  up 
in  a  wax  preparation,  enameled  wire  can  be  used,  thus  putting 
on  60%  more  turns  in  the  same  space.  The  insulating  prop- 
erty of  the  enamel  is  very  high  and  its  mechanical  strength  is 
great.  The  C.  E.  Cook  Electric  Company  of  this  city  handle 
this  wire  as  well  as  transformer  iron.  The  use  of  these  ma- 
terials will  increase  the  efficiency  of  the  transformer  very 
much,  on  account  of  the  lessened  resistance  for  the  same 
number  of  turns,  and  the  decreased  reluctance  of  good  iron. 
The  enamel  stands  a  high  degree  of  heat  without  injury.  The 
transformation  of  energy  is  not  due  to  the  flow  of  the  lines 
of  force  through  the  iron,  as  many  suppose,  but  it  is  due  to 
the  lines  of  force  being  compelled  to  cut  the  wires  of  the 
secondary,  on  account  of  the  fact  that  the  iron  offers  an  easy 
path  to  the  lines,  and  they  leave  the  air  to  reach  the  iron.  In 
doing  this  they  must  cut  the  secondary  wires.  However,  the 
iron  offers  an  easy  path  to  the  lines  and  it  does  assist  to  that 
extent  in  the  saving  of  energy  and  hence  in  its  transformation. 

26.  Ratio  of  Turns. — The  following  proportions  give  the 
relations  between  the  volts  and  amperes  in  the  primary  and 
secondary.  The  turns  in  the  primary  are  to  the  turns  in  the 
secondary  as  the  volts  in  the  primary  are  to  the  volts  in  the 
secondary.  The  turns  in  the  primary  are  to  the  turns  in  the 
secondary  as  the  amperes  in  the  secondary  are  to  the  amperes 
in  the  primary;  or, 

Tp:Ts::Ep:Es,  and   Tp:Ts::Is:Ip, 

where  Tp  is  turns  in  the  primary ;  Ts,  turns  in  the  second- 
ary ;  Ip,  amperes  in  the  primary ;  and  Is,  amperes  in  the  sec- 
ondary. 

The  opposition  that  the  iron  offers  to  the  flow  of  the 
lines  of  force  is  called  reluctance.  The  reluctance  increases  as 
the  length  of  the  iron  increases  and  it  decreases  as  the  area 


HIGH  FREQUENCY  ELECTRICITY  147 

of  the  cross  section  of  the  iron  increases.  From  this  it  follows 
that  more  iron  must  be  used,  if  the  iron  is  poor,  like  common 
sheet  iron,  in  order  to  get  a  reasonably  efficient  transformation 
of  energy.  The  iron  should  be  greater  in  cross  section  and 
not  in  length. 

27.  Eddy  Currents  and  Hysteresis. — The  iron  should  be 
laminated  in  order  to  overcome  the  eddy  currents.     When  a 
current  of  electricity  circulates  in  the  primary,   it  induces   a 
current  in  the  iron  core  parallel  to  it  and  in  the  opposite  di- 
rection.    These  currents  will  heat  the  core  and  cause  great 
loss  of  energy. 

Each  time  the  current  reverses,  the  molecules  of  the  iron 
turn  end  for  end.  In  doing  so  they  rub  against  one  another 
and  the  friction  causes  heating.  This  is  known  as  hysteresis. 
Further,  the  molecules  do  not  come  completely  back  to  the 
neutral  point  and  it  requires  expenditure  of  energy  on  the  part 
of  the  lines  of  force  to  turn  them  back  to  the  neutral  point 
before  turning  them  in  the  new  direction.  This,  combined 
with  the  above,  is  known  as  hysteresis.  The  better  the  grade 
of  iron,  the  more  easily  the  molecules  turn  and  hence  the  less 
the  hysteresis  loss. 

28.  The  Air  Core  Transformer. — In  the  air  core  trans- 
former the  lines  of  force  pass  entirely  through  the  air.    On  ac- 
count of  the  reluctance  of  the  air,  the  losses  are  large  and  the 
transformation  of  the  energy  is  very  inefficient,   at  ordinary 
frequencies.     If  the  lines  of  force  are  caused  to  rise  and  fall 
with  great  speed,  the  efficiency  of  the -transformation  is  there- 
by raised.    This  occurs  in  the  case  of  high  frequency  currents. 
The  presence  of  iron  in  high  frequency  current  transformers 
cuts  no  figure,  because  the  molecules  of  the  iron  do  not  have 
time  to  turn.     Consequently  the  iron  is  like  so  much  air  or 
wood  so  far  as  the  lines  of  force  are  concerned. 

Ordinary  iron  becomes  saturated  when  all  the  molecules 
are  turned  with  their  poles  in  the  same  direction.  When  this 
state  is  reached,  it  is  a  waste  of  energy  to  use  more  magne- 


148  WIRELESS  TELEGRAPHY  AND 

tizing  current.  Hence  a  transformer  must  have  large  enough 
cross  section  to  carry  the  lines  of  force  at  low  .density. 

The  air  core  transformer  does  not  transform  the  energy 
of  the  primary  into  an  equivalent  amount  of  energy  in  the 
secondary.  A  large  part  of  it  is  transformed  into  waves  in 
the  ether.  These  waves  are  radiated  and  are  a  loss  to  the 
transformer.  As  the  lines  of  force  in  the  .primary  rise  and  fall 
the  waves  are  produced. 

In  the  case  of  the  iron  core  transformer,  the  lines  of  force 
rise  but  do  not  fall  back  into  the  primary.  They  rise  and 
rotate  over  into  the  iron  through  which  they  circulate.  Thus 
the  true  oscillation  is  destroyed,  and  no  waves  are  set  up  in  the 
ether. 


HIGH  FREQUENCY  ELECTRICITY  149 

CHAPTER  IX. 

THEORY    OF    RADIOTELEGRAPHY. 

1.  The  Current. — In  the  diagram  shown  in  Fig.  48, 
AKPR  is  the  primary  circuit  of  the  transformer,  A  is  the 
alternator  or  source  of  alternating  current,  K  is  the  sending 
key,  and  R  is  a  water  rheostat  for  regulating  the  flow  of  the 
current.  The  proper  use  of  the  regulating  rheostat  cannot  be 
overestimated.  The  amateur  and  even  the  professional  are 
very  apt  to  assume  that  the  distance  they  can  send  depends 
upon  the  amount  of  current  that  flows  in  the  primary  of  the 
transformer.  They  think  that  a  loud  spark  at  Si,  and  a  noise 
that  can  be  heard  several  blocks,  mean  powerful  oscillations 
and  great  sending  power.  This  is  a  great  mistake. 

The  amount  of  current  to  allow  in  the  primary  depends 
entirely  upon  the  inductance  and  .capacity  of  the  aerial;  in 
fact,  it  is  a  matter  of  tuning.  This  can  be  determined  readily 
by  experiment.  The  primary  turns  P  have  a  very  low  resist- 
ance, and,  if  it  were  not  for  the  inductance  of  the  coil  P,  which 
is  very  greatly  increased  by  the  presence  of  the  iron  core  of 
the  transformer,  an  immense  current  would  flow,  when  the 
key  K  is  closed  and  the  water  rheostat  cut  out.  But  owing 
to  the  presence  of  the  iron,  the  reaction  due  to  the  inductance 
chokes  back  the  current  and  but  very  little  current  flows  as 
long  as  the  secondary  is  open. 

When  the  secondary  is  closed,  howrever,  a  current  flows; 
and  the  current  that  flows  in  the  primary  depends  upon-  the 
resistances  and  reactances  of  the  secondary.  If  the  resistance 
of  the  secondary  be  low,  an  immense  current  flows  in  the 
primary,  with  a  corresponding  flow  in  the  secondary  and  the 
transformer  is  burned  out. 

SCi  is  the  secondary  circuit  in  which  Ci  is  a  condenser. 
The  amount  of  current  that  flows  in  the  secondary  depends 
upon  the  capacity  of  this  condenser.  The  secondary  coils  S 
have  a  high  resistance,  but  there  is  a  high  voltage  also  de- 
veloped in  the  secondary,  and,  if  the  secondary  be  shorted,  a 
current  flows  that  may  prove  dangerous  to  the  "transformer. 


150  WIRELESS  TELEGRAPHY  AND 

If  this  current  is  allowed  to  flow  long,  it  is  liable  to  burn  out 
the  transformer. 

When  the  secondary  is  connected  through  Ci  it  is  not 
shorted.  If  Ci  is  a  small  capacity,  only  a  small  current  flows. 
The  greater  the  resistance  of  S,  the  longer  the  time  it  takes 
to  charge  Ci ;  and  the  greater  the  capacity  of  Ci,  the  greater 
the  rate  of  flow  of  the  current.  If  the  condenser  is  not  put 
up  in  oil,  the  current  oscillates  back  and  forth  through  Ci 
with  a  humming  noise,  with  a  frequency  of  50  or  60  cycles 
per  second. 

The  current  pours  into  and  accumulates  in  Ci  until  its 
potential  rises  to  that  of  the  charging  current.  Suppose  that 
in  this  case  it  is  10,000  volts.  If  Ci  is  not  in  oil,  a  waste  of 
energy  occurs.  The  condenser  fills  and  a  spray  discharges  into 
the  air  all  around  the  edges  of  the  plates.  This  loss  of  energy 
can  be  stopped  by  putting  the  condenser  in  oil.  The  effect  of 
this  leakage  is  to  increase  the  capacity  of  the  condenser,  but 
to  its  disadvantage. 

If  the  plates  of  the  condenser  be  too  thin,  the  current  also 
leaks  through  the  plates,  which  injures  the  efficiency  and  oper- 
ation of  the  transformer.  To  secure  the  best  results,  the 
plates  should  be  made  of  heavy  quartz  glass  and  they  should 
be  immersed  in  oil.  If  the  glass  plates  are  thin,  the  high 
voltage  may  puncture  them. 

The  greater  the  capacity  of  the  condenser  Ci,  the  greater 
the  current  that  flows  in  the  secondary,  and  consequently  in 
the  primary.  This  causes  the  potential  difference  across  the 
primary  P  to  fall,  and,  if  too  large  a  current  flows,  arcing 
occurs  in  the  spark  gap  Si. 

CiSiC  is  the  closed  oscillation  circuit,  in  which  Si  is  the 
spark  gap  and  C  is  the  inductance  or  tuning  coil. 

When  the  condenser  is  charged,  if  Si  is  properly  adjusted, 
a  spark  jumps  across  Si  and  oscillations  take  place  in  the 
closed  oscillating  circuit"  CiSiC. 

The  current  rushes  first  into  one  side  of  the  condenser 
and  then  into  the  other,  gradually  dying  out.  The  frequency 
of  these  oscillations  depends  upon  the  relation  between  the 
capacity  of  the  condenser  and  the  inductance  of  the  coil.  It 


HIGH  FREQUENCY  ELECTRICITY  151 

also  depends  upon  the  time  that  it  takes  to  charge  the  con- 
denser through  the  resistance  of  the  secondary  5\  If  this 
resistance  be  too  large,  no  oscillations  occur;  hence,  the  lower 
the  resistance  in  S,  the  better. 

If  too  little  condenser  be  used,  no  oscillations  take  place 
and  an  arc  forms  at  5*7.  If  too  much  condenser  be  used,  the 
sparking  distance  is  cut  down.  If  too  much  current  flows,  the 
energy  is  wasted  in  two  ways.  First,-  an  arc  forms  at  Si  and 
destroys  the  oscillations,  and  since  oscillations  are  necessary  to 
the  formation  of  electromagnetic  waves,  this  proves  fatal. 

This  usually  occurs  when  too  little  condenser  is  used  and 
too  much  current  is  allowed  to  flow  in  the  transformer.  To 
remedy  it,  cut  down  the  current  and  use  more  condenser. 
Second,  if  too  much  current  is  allowed  to  flow  and  enough 
condenser  is  used  to  handle  it,  the  closed  oscillation  circuit  is 
out  of  resonance  with  the  open  oscillation  circuit  of  the  aerial, 
and  the  result  is  poor.  To  remedy  this,  cut  down  the  current 
and  the  condenser. 

If  this  is  not  done,  the  spark  Si  is  large  and  makes  a  great 
noise,  but  its  energy  is  wasted  in  heat.  The  use  of  the  right 
amount  of  current  is  one  of  the  most  difficult  things  for  both 
the  professional  and  amateur  to  learn. 

In  the  manner  here  described,  the  amount  of  current  used 
affects  the  tuning,  and  hence  it  becomes  a  factor  in  it.  In 
Fig.  j8,  IHDCEG  is  called  the  open  oscillating  circuit.  G  is 
the  ground,  H  is  the  anchor  gap,  /  is  the  aerial,  and  C  the 
tuning  helix.  For  the  complete  tuning  it  is  necessary  to  regu- 
late the  rheostat  R,  the  capacity  Ci,  the  spark  gap  Si  and  the 
inductance  C. 

The  frequency  of  the  oscillations  can  be  controlled  largely 
by  the  spark  gap.  When  the  spark  gap  is  wide  open,  the  fre- 
quency is  low,  and  when  the  gap  is  small,  the  frequency  is  high. 

These  various  factors  should  be  adjusted  until  the  maxi- 
mum result  is  obtained  in  the  anchor  gap  H.  The  spark  at  H 
should  be  white,  sharp  and  regular.  The  sound  emitted  by  Si 
should  be  musical,  neither  ragged  and  harsh,  nor  hissing.  If 
the  spark  H  be  too  fat,  and  has  too  much  energy  in  it,  it 
is  probably  due  to  arcing  and  the  oscillations  are  killed,  no- 


152 


WIRELESS  TELEGRAPHY  AND 


waves  being  set  up  in  the  ether  under  these  conditions.  Os- 
cillations without  arcing  are  necessary  to  the  production  of 
electromagnetic  waves  and  anything  that  causes  arcing  pre- 
vents them.  Furthermore,  when  arcing  occurs,  the  system  is 
out  of  tune. 

The  closed  oscillation  circuit  is  a  persistent  oscillator,  but 
a  poor  radiator.  The  open  oscillation  circuit  is  a  poor  oscil- 
lator, but  a  good  radiator  of  electromagnetic  waves. 

2.  Tuning. — In  order  to  produce  good  radiations  in  the 
open  oscillating  circuit,  however,  it  is  necessary  for  the  closed 
oscillating  circuit  to  be  in  tune  with  the  open  oscillating  cir- 
cuit ;  otherwise  they  interfere  with  one  another. 

The  process  of  tuning  consists  in  adjusting  the  capacity 
and  inductance  so  that  they  offset  one  another.  The  current 
then  flows  according  to  Ohm's  law.  As  has  been  before  pointed 
out,  the  back  E.M.F.  of  the  capacity  is  180  degrees  from  the 
back  E.M.F.  of  the  inductance,  and  hence  if  they  are  properly 
adjusted  they  offset  one  another.  Furthermore,  the  condenser 
is  charging  and  discharging.  If  everything  is  in  resonance, 
the  condenser  discharges  and  charges  so  that  the  charging  and 
discharging  current  act  together.  If  the  condenser  attempts 
to  charge  while  the  oscillations  are  going  on,  the  pressure  of 


"G 


Fig.   77.     Method  of  tuning  open  oscillation   circuit   to   current   used. 


HIGH  FREQUENCY  ELECTRICITY  153 

the  charging  current  may  be  exerted  against  the  pressure  of  the 
oscillations  and  the  result  is  a  decrease  in  both  of  them. 

If,  however,  the  charging  current  be -always  coming  in 
one  side  of  the  condenser  when  the  oscillating  current  is  com- 
ing in,  then  they  assist  one  another.  This  result  can  be 
brought  about  by  adjusting  the  factors  involved. 

It  is  like  a  swing.  If  the  swing  be  pushed  as  it  is  ap- 
proaching, its  motion  is  stopped,  but  if  it  be  pushed  just  as  it 
reaches  the  highest  point  of  its  swing,  it  is  assisted  instead  of 
being  retarded,  and  at  each  push  it  swings  higher  and  higher. 

3.  Tuning  the  Open  Oscillation  Circuit. — The  open  os- 
cillation circuit  consists  of  the  aerial  E,  Fig.  77,  the  anchor 
gap  H,  the  tuning  inductance  IM,  the  spark  gap  Si  and  the 
ground  G.  The  condenser  in  this  system  consists  of  the  part 
of  the  system  above  Si  for  one  plate,  and  the  part  SiG  for 
the  other  plate,  the  air  being  the  dielectric.  If  a  transformer 
T  be  connected  across  the  spark  gap  Si,  the-  aerial  and  the 
ground  charge  the  same  as  any  condenser.  If  the  spark. gap 
Si  is  properly  adjusted,  a  spark  passes  and  oscillations  take 
place  in  the  aerial. 

As  the  corpuscles  rush  back  and  forth,  they  set  up  waves 
in  the  ether,  that  radiate  in  all  directions.  In  this  case  no 
condenser  needs  to  be  used  in  the  closed  oscillation  circuit 
SBSiN. 

The  capacity  of  the  aerial  is  small  and  an  open  circuit 
like  this  is  not  a  persistent  oscillator,  but  this  arrangement 
can  be  used  in  order  to  tune  the  open  oscillation  circuit  by 
adjusting  the  water  rheostat  R  and  the  inductance  MI,  the 
capacity  of  the  aerial  being  fixed,  until  a  maximum  result  be 
obtained. 

To  the  ordinary  receiving  set  already  described  attach  an 
aerial  /  long  enough  to  be  brought  parallel  to  the  inductance 
IM.  Across  the  phones  X  shunt  a  potentiometer  FV .  This  po- 
tentiometer should  contain  a  slide  wire  resistance  in  series  with 
the  larger  resistances  of  the  phones.  The  current  from  the 
detector  D  divides  between  the  phones  and  the  potentiometer. 
If  the  sliding  contact  0  be  at  F,  the  phones  are  shorted  out 
and  no  sound  is  heard  in  them.  If  the  point  0  be  moved 


154 


WIRELESS  TELEGRAPHY  AND 


toward    V,   then   more   and   more   of   the   current   is   shunted 
through  the  phones. 

In  order  to  tune  the  open  oscillating  circuit,  set  the  ap- 
paratus to  going  by  closing  the  key  K.  Adjust  Si  until  a 
spark  passes.  Adjust  R  until  a  maximum  result  is  obtained 
in  the  phones  P.  When  the  sparks  are  passing  at  Si,  the 
aerial  radiates  waves.  When  these  waves  cut  7,  they  set  up 
a  current  in  7  which  oscillates  in  the  closed  circuit  LCD.  If 
the  point  0  be  moved  toward  F,  a  point  is  reached  where  no 
sound  is  heard  in  the  phones  X.  The  stronger  the  oscillations 
are  in  LCD,  the  nearer  0  must  be  moved  to  F  in  order  to 
have  the  phones  X  silent.  Adjust  the  contacts  L  and  C  and 
the  resistance  R  until  0  is  the  nearest  possible  to  F.  Then 
the  maximum  result  is  being  obtained.  By  adjusting  R,  L, 
C  and  0  until  a  maximum  result  is  obtained,  which  will  be 
when  0  is  the  nearest  to  F,  the  right  current  for  the  capacity 
of  the  aerial  can  be  found.  The  right  amount  of  current  is 
then  flowing  for  the  capacity  and  inductance  of  the  aerial. 


Fig.  78.     Method  of  tuning  closed  oscillation  circuit  to  open 
oscillation    circuit. 

If  the  oscillations  be  too  strong  and  cannot  be  tuned 
out  by  shortening  the  telephones,  move  7  farther  and  farther 
away  from  /  until  this  can  be  accomplished.  If  the  telephones 
prove  to  be  too  sensitive,  replace  them  with  a  vacuum  or  a 
Crooke's  tube. 

These  tubes  can  be  obtained  for  fifty  or  seventy-five  cents. 


HIGH  FREQUENCY  ELECTRICITY  155 

When   everything  is   in   resonance,   the   tube  glows   brightly. 
Adjust  as  described  above  until  it  glows  its  brightest. 

When  using  the  telephones  it  will  be  necessary  to  muffle 
the  spark  gap,  or  to  make  JL  long  enough  to  get  farther  away. 

3.  Tuning   the   Closed   Oscillation   Circuit. — The   closed 
oscillation  circuit  can  be  tuned  as  shown  in  Fig.  78.    Use  the 
same   sending  helix  MI  as  used  in  tuning  the   open  circuit. 
Arrange  the  receiving  set  in  the  same  manner  as  in  Fig.  //. 
See  that  the  aerial  /  is  at  the  same  distance  from  MI  as  in  the 
previous  experiment.     Place  the  contacts  L  and  C  at  the  same 
point  that  they  had  in  the  previous  circuit.     Adjust  R,  Ci  and 
Si  until  a  maximum  result  can  be  obtained  in  the  phones  as 
described  in  the   previous  experiment.     When   this   result   is 
reached,  the  closed  circuit  will  have  the  same  time  period  that 
the   aerial   circuit   has.      Couple   them   together   as   shown   in 
Fig.  48,  and  they  will  work  at  their  best,  for  they  are  in  tune. 

This  method  of  tuning  will  not  require  a  hot  wire  am- 
meter nor  any  other  apparatus  besides  the  apparatus  used  in 
sending  and  receiving.  When  this  is  done,  the  current  that 
is  running  in  the  primary  is  the  greatest  that  should  be  used 
with  the  aerial  as  tested.  If  it  be  desired  to  send  further  by 
using  more  energy,  put  more  wire  in  the  aerial  by  increasing 
its  height  or  by  putting  up  more  wires  in  parallel. 

If  the  tuning  coil  is  calibrated,  the  wave  length  of  the 
aerial  can  be  found  in  this  way.  The  calibration  of  the  tuning- 
coil  will  be  described  later. 

The  shunting  of  the  potentiometer  across  the  phones  in 
order  to  determine  the  strength  of  the  incoming  signals  was 
due  to  Capt.  Wiseman  of  the  U.  S.  Army.  The  relative 
strength  of  signals  from  different  stations  can  be  easily  de- 
termined in  this  way.  The  point  0  is  moved  toward  F  until 
the  phones  are  silent,  and  the  nearer  they  can  be  moved  the 
stronger  the  incoming  signals. 

4.  Oscillations. — When   oscillations   are   taking  place   in 
the  aerial,  corpuscles  are  rushing  back  and  forth  across  the 
spark  gap  from  the  aerial  to  the  ground,  and  back  again  from 


156 


WIRELESS  TELEGRAPHY  AND 


the  ground  to  the  aerial.  The  first  discharge  is  strong,  but 
each  successive  oscillation  is  weaker  than  the  preceding,  and 
they  finally  die  out.  These  oscillations  are  called  damped  or 
unsustained  oscillations. 

Each  discharge  of  the  condenser  sends  out  a  damped  os- 
cillation. These  follow  one  another  at  regular  intervals.  They 
are  called  a  train  of  oscillations  or  jigs. 


Fig.  79.     Highly  damped  train  of  waves. 


Fig.  79  shows"  a  train.  Each  jig  represents  one  condenser 
discharge.  The  higher  the  frequency,  the  nearer  these  jigs 
are  together,  and  the  more  nearly  the  oscillations  are  like  the 
sustained  oscillations  of  the  direct  current,  used  in  wireless 
telephony. 

.  As  the  corpuscle  rushes  up  the  aerial  it  tangles  with  the 
ether  in  some  way  unknown  and  sets  up  a  wave  in  it,  which 
radiates  out  in  all  directions  perpendicular  to  the  direction 
of  the  movement  of  the  corpuscle.  Lines  of  force  swell  out 
around  the  conducting  wire,  and  the  corpuscles  in  giving  mo- 
tion to  the  ether  lose  motion  in  the  exact  proportion  as  they 
give  it  to  the  ether. 

When  they  lose  sufficient  motion,  they  go  back  to  the 
atoms  from  whence  they  came. 


Fig.  80 


HIGH  FREQUENCY  ELECTRICITY 


157 


5.  Formation  of  a  Wave. — The  exact  phenomena  that 
takes  place  around  an  aerial  is  complicated.  In  Fig.  80,  let 
BC  be  the  aerial  above  the  spark  gap  B,  and  BG  the  part  below, 
the  ground  being  a  part  of  the  aerial.  When  the  corpuscle 


B 


E/- 


Fig.  82 

rushes  from  B  to  C,  it  executes  one-quarter  of  its  swing,  C 
being  the  top  of  the  aerial.  In  passing  from  B  to  C,  the  line 
of  force  ADE  swells  out  from  the  aerial  wire  as  a  center  and 
the  point  E  of  the  line  of  force  traces  the  quarter  wave  BE. 


158  WIRELESS  TELEGRAPHY  AND 

Since  BC  is  one-quarter  of  the  swing  of  the  corpuscle,  it 
is  easily  seen  why  the  aerial  is  one-quarter  the  wave  length 
emitted  by  it.  As  the  corpuscle  swings  back  to  B,  the  line  of 
force  CDE  falls  in  upon  the  aerial,  BE  is  pushed  on  to 
the  position  EM,  and  another  quarter  of  the  wave  is  formed 
at  BE. 

As  the  corpuscle  rushes  across  the  gap  into  the  ground, 
the  portion  MK  of  the  wave  is  formed  and  BEM  is  pushed 
on  into  the  position  MEB,  shown  in  Fig.  81.  As  the  corpuscle 
rushes  back  to  the  spark  gap,  the  portion  KN  is  formed,  and 
in  forming  the  portion,  KMEB  is  pushed  on  into  the  position 
shown  in  Fig.  82,  thus  forming  one  wave. 

The  line  of  force  ADE  has  its  plane  perpendicular  to  the 
aerial.  The  wave  BEMKN,  Fig.  80,  has  its  plane  perpendicular 
to  ADE. 

Thus  one  wave  length  after  another  is  formed  as  the 
corpuscle  rushes  back  and  forth  from  the  ground  to  the  aerial 
and  from  the  aerial  to  the  ground. 

A  stationary  wave  ONV  is  also  set  upon  the  aerial,  as 
shown  ONV,  Fig.  82. 

The  upper  part  of  the  wave  MEB,  Fig.  82,  thus  loops  on 
the  ground  and  runs  along  the  ground.  The  ground  is  a 
conductor,  and  the  free  ends  of  a  wave  or  a  line  of  force  always 
terminate  upon  a  conducting  surface.  This  is  why  the  wave 
follows  the  curvature  of  the  earth  instead  of  rushing  in  a 
straight  line  off  into  space. 

In  the  upper  atmosphere  the  air  is  very  thin.  Very  thin 
air  is  a  good  conductor  of  electricity  and  so  is  the  ground. 
Many  other  waves  are  formed  by  the  aerial  and  radiated  in 
all  directions.  Many  of  them  are  formed  like  the  stationary 
wave  ONV,  and  the  free  ends  of  this  wave  are  found  in  the 
conducting  upper  layer  and  the  ground.  They  thus  follow 
the  curvature  of  the  earth.  Since  the  aerial  and  ground  form 
a  condenser,  the  rise  and  fall  of  the  electrostatic  lines  around 
the  spark  gap  B,  as  shown  in  Fig.  83,  also  set  up  trains  of 
waves.  The  phenomena  is  very  complicated. 

Whenever  lines  of  force  or  waves  cut  conductors  perpen- 
dicularly, they  set  up  currents  in  these  conductors.  The  line 


HIGH  FREQUENCY  ELECTRICITY 


159 


Fig.  83.     Diagram  of  lines  of  stress  around  a  spark  gap. 

of  force  or  the  waves  are  real,  and,  as  they  cut  the  wire,  they 
tear  loose  the  corpuscles  from  the  atoms  and  set  them  to 
moving  in  the  wire. 

This  current  coming  down  the  aerial  through  the  detector 
to  the  ground  oscillates  back  and  forth  between  the  aerial  and 
the  ground.  This  oscillation  through  the  resistance,  offered 


Fig.  84.     Diagram   of  waves   emitted   by  an   aerial.      BCD,   the   upper 
part  of  the  wave  only,  is  effective  in  producing  current  in  L. 

by  the  detector,  shunts  some  of  the  current  through  the  phones 
and  consequently  a  noise  is  heard  in  the  telephone. 

Fig.  84  gives  a  graphic  representation  as  to  how  the 
energy  is  transmitted  from  the  transmitting  station  to  the 
receiving  station.  The  electricity  oscillating  in  the  receiving 
station  is  not  the  same  electricity  that  oscillates  in  the  sending 


160  WIRELESS  TELEGRAPHY  AND 

station.  If  B  be  the  spark  gap  of  the  transmitting  station 
sending  out  the  wave  BCDEF,  etc.,  and  if  OLG  be  the  receiving 
aerial,  then  the  wave  cutting  the  receiving  aerial  at  0  tears 
loose  the  corpuscles  at  O,  and  presses  them  down  the  wire 
through  the  detector  L,  the  free  ends  of  the  semi-waves  loop- 
ing in  the  ground. 

6.  Telegraphing  to  Mars. — It  is  very  improbable  that  any 
electromagnetic  waves  set  up  by  man  ever  get  outside  of  our 
atmosphere.  The  conducting  layer  of  the  upper  atmosphere 
absorbs  their  energy  and  thus  prevents  them  from  reaching 
any  further.  Whenever  an  electromagnetic  wave  cuts  a  con- 
ductor, it  sets  up  a  current  in  it,  and  the  energy  of  the  wave 
is  absorbed.  Its  motion  is  given  to  the  corpuscles  of  elec- 
tricity, torn  loose  from  the  atoms,  and  in  the  proportion  that 
the  corpuscles  are  given  motion,  in  that  same  proportion  do  the 
waves  lose  motion. 

The  upper  layers  of  the  atmosphere  are  very  good  con- 
ductors of  electricity.  The  air  here  is  in  the  condition  of  the 
air  in  a  Crooke's  tube.  The  powerful  electromagnetic  waves 
from  the  sun  can  penetrate  this  layer,  as  all  of  their  motion 
is  not  absorbed,  but  the  comparatively  weak  waves  set  up  by 
man  can  not,  and  their  motion  is  probably  absorbed. 

If  this  be  true,  communication  by  wireless  with  the  in- 
habitants of  Mars  is  impossible.  Even  if  we  were  able  to  set 
up  waves  powerful  enough  to  get  through  our  atmosphere, 
these  waves  would  have  to  meet  the  same  conditions  in  the 
atmosphere  of  Mars,  and,  since  the  strength  of  the  radiation 
decreases  with  the  square  of  the  distance,  the  waves  would 
be  very  weak  upon  their  arrival,  and  they  would  suffer  ab- 
sorption. 

Referring  again  to  Fig.  84,  the  only  part  of  the  wave 
BCDF  that  is  effective  in  setting  up  current  in  OLG  is  the  part 
BCD.  The  part  DEF  is  absorbed  by  the  ground.  Since  the 
ground  is  a  conductor,  the  motion  of  the  wave  is  changed  into 
motion  of  corpuscles  of  electricity  in  the  ground,  and  hence 
all  of  the  wave  below  the  ground  is  lost.  If  this  wave  could 
be  rectified,  it  would  result  in  a  big  saving;  i.e.,  if  DEF  could 


HIGH  FREQUENCY  ELECTRICITY  161 

be  turned  over  and  made  to  occupy  the  gap  above  it,  it  would 
result  in  all  of  the  wave  cutting  OLG  instead  of  only  half  of  it. 

It  must  be  remembered  that  this  wave  shown  in  Fig.  84 
should  be  in  the  form  of  a  train  of  jigs  as  shown  in  Fig.  /p, 
the  upper  half  of  the  jigs  only  being  effective. 

The  wave  shown  in  Fig.  84  is  a  continuous  undamped 
wave.  This  can  be  produced  by  causing  the  direct  current 
to  oscillate.  It  is  then  called  an  undamped  wave. 


162  WIRELESS  TELEGRAPHY  AND 

CHAPTER  X. 

UNITS  AND  STATION  CALCULATION. 

1.  Force.  —  Force  is  a  pressure  exerted  by  matter  in  mo- 
tion.    In  many  cases  it  is  difficult  to  locate  the  motion  that 
is  the  cause  of  the  pressure,  the  force  of  gravitation  being  an 
instance. 

2.  Dyne.  —  The  unit  of  force  is  the  dyne.     A  force  that 
can  give  a  velocity  of  one  centimeter  per  second  to  a  mass 
of  one  gram  is  a  dyne.     This  is  a  very  minute  force. 

3.  Gram.  —  The  gram  is  the  unit  of  mass.     It  is  the  mass 
of  a  cubic  centimeter  of  pure  water   at  zero   degrees   centi- 
grade.   A  gram  of  force  is  equal  to  980  dynes. 

4.  Erg.  —  The  erg  is  the  unit  of  work.     It  is  the  work 
done  in  overcoming  a  force  of  one  dyne  continuously  through 
a  distance  of  one  centimeter. 

5.  Watt.  —  The  watt  is  the  unit  of  power  or  rate  of  doing 
work.     It  is  equal  to   10,000,000  ergs  per  second.     Watts  = 
volts  X  amperes. 

6.  Current.  —  The   absolute   unit   of   current,   represented 
by  /,  is  the  current  flowing  through  a  wire  one  centimeter  long, 
bent  into  an  arc  of  one  centimeter  radius  and  exerting  a  force 
of  one  dyne  upon  a  unit  magnetic  pole  at  the  center.     The 
ampere  represented  by  /  is  1/10  the  size  of  this  absolute  unit. 


_ 

10 

7.  Unit  Pole.  —  The  unit  magnetic  pole  is  one  that  repels 
an  exactly  similar  pole  with  a  force  of  one  dyne  at  a  distance 
of  one  centimeter. 


HIGH  FREQUENCY  ELECTRICITY  163 

8.  Voltage. — The  absolute  unit  of  pressure,  represented 
by  c,  is  the  work  in  ergs  necessary  to  carry  one  unit  quantity 
of  electricity  from  one  point  to  another  in  a  conductor  against 
the   resistances   existing  between   the   two  points.     The   volt 
represented  by  E  is  100,000,000  times  as  large.     E  =  10V. 

9.  The  Coulomb. — A  unit  quantity  of  electricity,  repre- 
sented by  q,  is  a  unit  current  flowing  for  one  second.     The 
practical   unit   is   the   Coulomb,   represented   by   Q,   which   is 
equal  to  one  ampere  for  one  second.     Q  =  It. 

10.  The   Ohm. — The   absolute  unit  of  resistance,   repre- 
sented by  r,  is  that  resistance  which  will  allow  one  absolute 
unit  of  current  to  flow  under  one  absolute  unit  of  pressure. 
The  practical   unit,  the  ohm,    is    represented    by    R.      It    is 
1,000,000,000  times  the  absolute  unit,  or  R  =  10V. 

From  the  above  definitions  the  current  in  amperes,  rep- 
resented by  /,  is  equal  to  the  voltage,  represented  by  E,  divided 
by  the  resistance  represented  by  R.  This  is  known  as  Ohm's 
law,  and  it  applies  to  the  direct  current  only  or  the  alternat- 
ing current  when  everything  is  in  resonance.  -,  E 

^^ 

11.  The  Farad. — The  farad  is  the  unit  of  capacity.     It  is 
that  capacity  that  one  coulomb  of  electricity  will  charge  to  a 
pressure  of  one  volt.     The  farad  is  very  large  and  the  micro- 
farad is  used.    Capacity  is  usually  represented  by  C.    Q  =  EC. 

12.  The  Henry. — The  henry  is  the  unit  of  inductance.    A 
henry  is  the  inductance  that  will  set  up  a  counter  E.M.F.  of 
one  volt  when  the  current  varies  at  the  rate  of  one  ampere  in 
one  second. 

13.  Ohm's  Law  for  the  Alternating  Current. — In  the  al- 
ternating current  both  capacity  and  inductance  have  an  effect 
upon  the  current  as  well  as  the  resistance  and  the  voltage. 
In  fact,  the  back  or  counter  pressures  due  to  these  factors  are 
really   so   much    resistance.      The   following   equation   applies 
to  the  alternating  current  instead  of  Ohm's  law. 


164  WIRELESS  TELEGRAPHY  AND 

(1)  /=-  E 


A,r,          0     T  1       we  have  resonance,  and  E 

When    2irnL=^ — -^  /  — — 

2-nnC    equation   (1)   reduces  to  R 


If    2-nnL  =  75  —  -p,     then 
2-jrnC 

4w2w2LC  =1      and 


or 


(2) 


2*^  LC 

Hence,  when  the  capacity  reactance  equals  the  inductive 
reactance,  there  is  resonance  and  equation  (2)  gives  the  fre- 
quency. In  the  above  formulas,  /  stands  for  amperes,  E  for 
volts,  R  for  resistance  in  ohms,  «  for  frequency  or  cycles  per 
second,  L  for  inductance  in  henries,  C  for  capacity  in  farads, 
and  TT  for  3.1416,  the  ratio  between  the  diameter  and  the 
circumference  of  a  circle.  The  V  LC  is  called  the  oscillation 
constant. 

The  farad  and  the  henry  are  very  large  units,  and  it  is 
necessary  to  use  smaller  ones.  The  prefix  micro  is  used,  mean- 
ing one-millionth,  and  the  prefix  milli,  meaning  one-thou- 
sandth. Thus  we  have  for  practical  units  the  microfarad  and 
the  microhenry. 

14.  Inductance.  —  The  inductance  of  a  wire  increases  di- 
rectly as  its  length,  and  hence  inductance  can  be  expressed  in 
centimeters.  A  straight  wire  1,000  centimeters  long  has  one 
microhenry  of  inductance,  one  1,000,000  centimeters  long  has 
one  millihenry  of  inductance,  and  one  1,000,000,000  centimeters 
long  has  one  henry  of  inductance. 

A  current  rising  at  the  rate  of  one  ampere  per  second 
will  cause  a  back  E.M.F.  of  one  volt  in  a  wire  1,000,000,000 
centimeters  long.  This  is  equal  to  a  wire  equal  in  length  to  a 
quadrant  of  the  earth's  surface.  1,000  centimeters  is  equal  to 


HIGH  FREQUENCY  ELECTRICITY  165 

10  meters,  or  about  33  feet.     A  wire  10  meters  long  will  have 
one  microhenry  of  inductance. 

If  these  wires  be  curved  into  helices,  their  inductances  are 
largely  increased. 

15.  Station  Calculation. — The  capacity,  inductance,  fre- 
quency and  oscillation  constant  of  the  closed  oscillation  circuit 
can  be  calculated  roughly. 

When  the  closed  oscillation  circuit  is  tuned  to  the  open 
or  radiating  circuit,  constituting  the  aerial,  the  oscillation  con- 
stant of  the  two  is  the  same,  hence  the  radiated  wave  length 
can  be  calculated,  if  the  constants  of  the  closed  circuit  be 
known. 

The  following  equation  gives  the  relation  between  the  ve- 
locity of  a  wave,  v\  its  frequency,  n;  and  the  wave  length,  w. 

(3)  v  =  nw 

Substitute  the  value  of  n  in  equation  (2)  in  place  of  n  in 
equation  (3),  then 

w 

v  = or 

27T  y  LC 

(4)  w  =  2irv  ^/~LC 

Since  v  =  300,000,000  meters  per  second,  the  velocity  of 
all  waves  in  the  ether,  w  can  be  computed  when  L  and  C  are 
known.  300,000,000  can  be  written  3  X  108,  read  3  times  10 
to  the  eighth  power.  1  with  8  ciphers  after  it  means  10 
multiplied  by  itself  8  times.  Remember  that  10  X  10  is  ten 
used  twice  and  equals  102. 

In  equation  (4),  L  is  expressed  in  henries  and  C  in  farads. 
It  is  more  convenient  to  express  them  in  microfarads  and 
microhenries  or  centimeters.  1,000,000  microfarads  equals  one 
farad,  and  1,000,000  microhenries  equals  one  henry. 

If  C  represents  farads  and  we  call  it  microfarads,  we  have 
multiplied  the  number  that  C  stands  for  by  1,000,000,  and 
hence  in  equation  (4)  we  must  divide  C  by  1,000,000  in  order 
to  make  it  as  it  was  before.  The  same  observation  applies  to 
the  inductance.  Hence, 


166  WIRELESS  TELEGRAPHY  AND 

W  T65" 

where  L  and  C  are  microhenries  and  microfarads ;  substituting 
300,000,000  for  v,  the  velocity  of  the  electromagnetic  wave  in 
the  ether,  and  taking  106  out  from  under  the  radicle,  (4a) 
becomes : 

-  ^~Tc 


=6*  X  102  V  LC 

It  is  convenient  to  have  microhenries  expressed  in  centi- 
meters. If  L  is  called  centimeters  in  the  above  equation,  it  is 
equivalent  to  multiplying  it  by  1,000,  and  hence  it  must  be 
divided  by  1,000  to  make  it  as  it  was  before.  Hence, 


IV  =  6-n-  > 

67T    X    IP' 

~~     31.62 


V  LC 


=  .596  X  102  V  LC 


=  59.6  V  LC 


Hence, 


(5)  w  =  59.6  V  LC   or   60  V  LC 

where  L  is  in  centimeters  and  C  is  in  microfarads. 

Equation  (2)  can  be  reduced  in  the  same  way 

f2)         n=  = 


10°    X    106 


J_  106 


HIGH  FREQUENCY  ELECTRICITY  167 

Where  L  is  microhenries  and  C  is  microfarads, 
_10°  106 

n  = 


9    ^  L     C 

2- 

\'  LC 

103  C 
5.033  X  106 

31.62  V  J 
or     AXiO.6 

(6) 

y  ^c  v  ££ 

where  L  is  in  centimeters  and  C  is  in  microfarads.  If  L  and 
C  can  be  measured  or  calculated,  then  the  frequency  and  wave 
length  can  be  easily  found. 

The  capacity  can  be  roughly  calculated  from  the  follow- 
ing: 

(7)  =  36^  X  105 

where  C  is  the  capacity  in  microfarads,  K  the  dielectric  con- 
stant of  the  insulating  plates  in  the  condenser.  For  air,  K  is 
1,  and  for  ordinary  glass  it  is  about  6.  5  is  the  area  of  the  tin 
foil  on  the  plates  in  square  centimeters,  d  is  the  thickness 
of  the  glass  in  centimeters. 

On  account  of  the  brush  discharge  in  a  condenser,  its  ca- 
pacity for  high  frequency  currents  is  from  five  to  ten  per 
cent  higher  than  the  calculated  value.  Hence,  the  value  as 
calculated  from  the  above  formula  is  from  five  to  ten  per  cent 
too  small.  The  greater  the  thickness  of  the  glass,  the  less 
accurate  the  formula  also.  This  formula  is  for  circular  plates. 
This  will  introduce  another  error  if  the  plates  are  square. 

It  can  thus  be  seen  that  this  calculation  of  capacity  is  only 
roughly  correct. 

If  the  diameter  of  the  plates  is  100  times  the  thickness 
of  the  glass,  the  calculated  capacity  is  about  2l/2%  ^ess  than 
the  real  capacity.  This  is  owing  to  the  leakage  of  the  lines  of 
force  around  the  ends  of  the  glass  plates.  Hence,  in  calculating 
capacity  from  this  formula,  from  10  to  15%  must  be  added  to 
make  up  for  these  errors. 

Condenser  plates  in  parallel  are  merely  added  together  in 
order  to  determine  their  combined  capacity.  If  the  plates  be 
in  series,  the  following  formula  must  be  used  to  determine 
their  combined  capacity: 


168  WIRELESS  TELEGRAPHY  AND 

C  =-7^  ~^r~  ^or  ^  plates 
r  r  r 

— ,  V-X    -I   V^    <>VX    O  r  S*  - 

C  =  y~  /-   _i_  /-  ^    _i_  r  r  plates 

1       2       I  1       3        I  2      3 


for  4  plates 


In  order  to  apply  this  formula,  multiply  all  of  the  ca- 
pacities together  to  form  the  numerator  of  the  fraction.  For 
the  denominator  form  as  ma'ny  groups  as  there  are  capacities 
in  the  numerator,  having  one  less  capacity  in  each  group  than 
is  found  in  the  numerator,  being  careful  not  to  repeat  the 
groups.  The  groups  of  the  denominator  are  added. 

The  groups  in  the  denominator  can  be  easily  formed  as 
follows :  Cover  one  capacity  of  the  numerator  with  the  finger 
and  multiply  the  rest  of  them  together  for  the  first  group  of 
the  denominator.  Cover  the  next  capacity  and  multiply  all 
the  others  together  for  another  group,  etc.,  until  each  capacity 
of  the  numerator  has  been  covered. 

The  inductance  in  centimeters  can  be  determined  by 
measuring  the  length  of  the  wire,  if  it  be  straight,  and,  if  it 
be  formed  into  a  helix,  the  following  formula  can  be  used  : 

(8)  L  =  l(7rDNy- 

Where  L  is  the  inductance  in  centimeters,  TT  is  3.1416; 
D  is  the  diameter  of  the  helix  in  centimeters ;  TV  is  the  number 
of  turns  per  centimeter  of  length  of  the  helix ;  /  is  the  length  of 
the  helix  in  centimeters.  ' 

The  value  of  L  as  found  by  this  equation  is  always  a  little 
too  large.  If  the  length  of  the  helix  is  50  times  its  diameter, 
the  value  is  correct  to  within  2%  or  3%  ;  if  100  times  as  long, 
it  is  correct  to  within  1%  to  2%.  The  longer  the  helix  and  the 
less  its  diameter,  the  more  nearly  correct  the  value.  In  a 
short  helix  with  a  large  diameter,  the  error  is  larger. 

Since  the  calculated  value  of  C  is  too  small  and  that  of 
L  is  too  large,  they  offset  one  another  to  a  certain  extent.  In 
any  case  the  calculated  value  is  a  rough  one.  If  the  plates 


HIGH  FREQUENCY  ELECTRICITY  169 

of  the  condenser  are  put  in  oil,  the  brush  discharge  is  stopped 
and  the  calculated  value  will  then  be  very  much  more  correct. 

In  order  to  give  a  concrete  example,  we  shall  proceed  to 
calculate  the  frequency  and  wave  length  of  the  station  located 
on  the  Los  Angeles  Polytechnic  High  School. 

Formulae  (5)  (6)  (7)  and  (8)  are  necessary  for  our  pur- 
pose. 

(8)  L^l^DN)2 

The  helix  has  the  following  dimensions :  The  length  /  is 
42.06  centimeters;  the  diameter  D  is  21.84  centimeters;  total 
turns  in  the  helix  is  22 ;  N,  the  number  of  turns  per  centi- 
meter, is  22  divided  by  42.06  =  .523. 

When  in  tune,  there  are  8  turns  included  within  the  closed 
oscillating  circuit.  Hence  8/22  X  42.06  is  15.2,  the  length  /. 

L  =  15.2(3.1416  X  21.84  X  -523)2 
=  15.2(35.88) 
=  19,568.02  centimeters. 

Since  the  helix  is  large  in  diameter  compared  with  its 
length,  we  shall  subtract  at  least  10%  as  a  correction,  giving 
17,611.22  centimeters  of  inductance. 

The  condenser  shown  in  Fig.  16  had  seven  plates  cut  in 
when  in  resonance.  Since  the  plates  are  in  parallel,  their 
capacity  is  their  sum.  If  we  take  K  as  6,  and  the  thickness  of 
the  plates  averages  .32  centimeters  as  found  by  measurement, 
then, 

(7)  c— — 

"      rd  X  105 

6(20.32  X  15.24)7 


36  X  3.1416  X  -32  X  105 

where  the  tin  foil  on  the  plates  measured  20.32  centimeters  by 
15.24  centimeters. 

This  gives  a  value  of  .00359  microfarads. 

Since  the  condenser  is  not  in  oil,  we  shall  add  12%  for 
corrections.  The  corrected  value  is  .003949  microfarads. 


170  WIRELESS  TELEGRAPHY  AND 


The  oscillation  constant  is  V  CL  or 


V  17,611. 22  X  -003949 


=  V  69.5467  ±=  8.34  or 


V  CL  =  8.34,  the  oscillation  constant  of  the  closed  oscillating 
circuit. 

Since  the  closed  oscillation  circuit  and  the  open  oscillation 
circuit  are  in  tune,  they  both  have  the  same  oscillation  con- 
stant. 

In  order  to  compute  the  wave  length,  use  formula 


(5)  w  =  60  V  CL 

=  60  X  8.34 

—  500  meters  practically 
By  formula 

5  V  10° 

(6)  n  =     *_U 

5  X  1,000,000 


8.34 

=  599,520  or  practically  600,000  cycles 
per  second. 


HIGH  FREQUENCY  ELECTRICITY  171 

CHAPTER  XL 

CALCULATION   OF  TRANSFORMERS. 

Transformers  are  calculated  by  the  aid  of  the  following 
formulae  : 

_     '       .  watts  output 

(9)  %  efficiency  =  — 

watts  input 

(10)  $ 


Where  Tp  =  turns  in  the  primary. 
E  =  volts  in  the  primary. 
n  =  frequency. 
<J>  =  total  lines  of  force. 

A  —  area  of  the  cross  section  of  iron  core. 
B  =  lines  of  force  per  square  inch. 

Small  transformers  are  lower  in  their  efficiency  than 
large  ones.  In  order  to  secure  the  best  efficiency  the  best 
kind  of  transformer  iron  should  be  secured: 

The  efficiencies  range  from  90%  in  small  transformers  to 
99%  in  the  largest  ones.  For  our  purpose  we  shall  choose  the 
kilowatt  size.  The  first  thing  to  determine  is  the  input  where 
we  desire  a  kilowatt  output.  We  shall  assume  an  efficiency  of 
94%.  Then, 

(9)  .94= 


watts  input 
and   watts   input  —  -^—  —  =  1,063.83 

The  watts  input  then  is  1,063.83,  and  the  difference  be- 
tween this  number  and  1,000  watts  gives  us  the  watts  loss, 
63.83  watts. 

This  loss  includes  the  total  losses  in  the  transformer. 
These  losses  are  made  up  of  core  losses  and  PR  losses.  The 
PR  losses  are  due  to  the  heating  effect  of  the  current  in  both 


172  WIRELESS  TELEGRAPHY  AND 

the  primary  and  the  secondary.  The  core  losses  include  the 
losses  occurring  in  the  core  due  to  hysteresis  and  eddy  cur- 
rents. 

From  experience  the  core  losses  are  found  to  be  about 
47 %  of  the  total  loss  and  the  PR  losses  53%. 

To  get  core  losses,  take  47%  of  63.83,  the  total  losses. 

.47  X  63.83  =  29.986  watts  core  loss 

To  get  hysteresis  loss,  take  80%  of  the  core  losses,  i.e., 
multiply  29.986  by  .80,  or  calling  29.986,  30,  since  it  is  nearly  so, 

.80  X  30  =  24  watts 

loss  due  to  hysteresis. 

The  eddy  current  losses  are  due  to  the  induced  currents 
in  the  iron.  The  resistance  of  the  iron  core  is  small,  and  hence 
the  currents  running  in  the  primary  set  up  currents  in  the  iron 
in  the  opposite  direction,  of  low  voltage  and  high  amperage. 

To  prevent  this,  the  iron  is  laminated,  and,  since  the  volt- 
age of  these  eddy  currents  is  low,  the  oxide  that  forms  on  the 
surface  of  the  iron  generally  presents  enough  resistance  to 
prevent  their  flow. 

The  hysteresis  losses  are  due  to  the  force  necessary  to 
turn  the  molecules  of  the  iron  first  one  way  and  then  the  other ; 
as  the  lines  of  force  flow  first  one  way  and  then  the  other 
way,  due  to  the  alternations  of  the  current. 

It  is  with  this  hysteresis  loss  that  we  are  particularly  con- 
cerned in  this  calculation. 

Table  III  gives  the  curve  which  shows  the  relation  between 
watts  loss  per  cubic  inch  for  50  cycles,  for  densities  ranging 
0  lines  per  square  inch  in  iron  to  40,000  lines  per  square  inch. 

The  hysteresis  losses  increase  with  the  density  at  which 
the  iron  is  worked.  The  reluctance  of  the  iron  increases  as 
the  density  at  which  the  iron  is  worked  increases,  hence  the 
greater  the  cross  section  of  the  iron,  the  better.  Increased 
cross  section  means  increased  amount  of  copper  wire,  and 
increased  losses  due  to  its  resistance.  The  cost  of  the  wire 
also  cuts  a  figure,  so  that  it  is  necessary  to  choose  a  cross 
section  that  strikes  a  mean  between  all  these  factors. 


HIGH  FREQUENCY  ELECTRICITY  173 

For  commercial  transformers  in  which  an  all-day  efficiency 
is  required,  the  density  should  not  run  above  20,000  lines  per 
square  inch  of  cross  section,  but  in  transformers  for  wireless 
work  an  all-day  efficiency  is  not  required.  30,000  lines  is  about 
right  for  our  purpose. 

Look  along  the  lower  line  in  Table  III  for  the  number 
30,000.  This  line  is  called  the  abscissa  or  the  axis  of  X. 

Having  found  this  number,  follow  the  perpendicular  line 
drawn  from  this  number  upward  until  the  curve  is  reached. 
From  the  point  where  this  line  cuts  the  curve,  follow  a  line 
horizontally  to  the  left,  until  it  cuts  the  line  of  ordinates  on  the 
extreme  left.  Here  the  number  .125  is  found.  This  means 
that  .125  watt  loss  occurs  for  each  cubic  inch  of  iron  that  there 
is  in  the  core  of  the  transformer,  when  it  is  worked  at  a  den- 
sity of  30,000  lines  per  cubic  inch,  and  at  a  frequency  of  50 
cycles. 

Since  we  are  designing  for  60  cycles,  we  must  multiply  this 
number  by  60/50. 

|^X  125  =  .I5  watts 

If  one  cubic  inch  suffers  a  loss  of  .15  watts,  how  many 
cubic  inches  will  it  require  to  handle  a  loss  of  24  watts 
due  to  hysteresis? 

24 

y-=-=zr  160  cu.  in.  of  iron. 

•  L  0 

The  dimensions  to  be  given  to  the  core  containing  160 
cubic  inches  is  next  to  be  determined.  It  will  not  do  to  give 
the  core  too  small  a  cross  section,  as  that  would  necessitate  a 
core  too  long,  which  would  require  more  turns  in  the  primary 
in  order  to  force  the  lines  of  force  through  the  great  reluctance. 
Experience  indicates  that  the  core  should  have  a  cross  section 
of  about  four  square  inches.  In  order  to  make  it  convenient 
for  winding,  we  will  make  the  core  square,  thus  making  it 
2  inches  thick  and  2  inches  wide. 

The  other  dimensions  of  the  core  depend  upon  the  voltage 
desired  in  the  secondary,  and  also  upon  the  amount  of  money 
one  can  put  into  the  transformer.  The  only  way  to  do  is  to 


174 


WIRELESS  TELEGRAPHY  AND 


assume  some  values  and  try  them ;  if  they  cannot  be  made  to 
fit,  try  another  set  of  values,  For  our  purpose  here  we  shall 
make  the  core  longer  than  it  is  wide.  If  we  divide  160  by  4, 
the  area  of  the  cross  section,  we  have  40  inches  for  combined 
length  of  the  ends  and  the  sides.  If  we  make  the  core  15 
inches  long  and  8%  inches  wide,  outside  measure,  it  is  about 
right.  In  order  to  arrive  at  this,  assume  various  values  for 
the  length  and  the  width.  See  whether  the  width  and  length 
will  accommodate  the  windings.  If  not,  try  again.  By  refer- 
ring to  Fig.  85,  we  can  determine  whether  this  will  suit  our 
purpose.  Compute  the  amount  of  iron  with  the  assumed 
values. 


00 


space 


Fig.  85.     Dimensions  of  kilowatt  transformer. 

A,  primary  leg;  B,  secondary  leg;  W,  primary  wire;   C,  secondary 
wire;   E,  empire  cloth  insulation. 

Length  around  core  ==  15  +  15+  4J4  +4^4  =  38.5. 

Width  of  core,  2  inches. 

Thickness  of  core,  2  inches. 

Hence,  2\  2  X  38.5  =  154  cubic  inches. 


HIGH  FREQUENCY  ELECTRICITY  175 

This  is  close  enough  to  160  to  do.  It  is  now  necessary 
to  determine  the  total  lines  of  force  that  will  thread  through 
this  cross  section  at  30,000  lines  to  the  square  inch.  Use 
formula 


(10)  (f> 

c/>  =  2  x  2  X  30,000  =  120,000 

for  total  lines  of  force. 

Formula  (11)  is  used  for  the  purpose  of  determining  the 
number  of  turns  of  wire  in  the  primary  necessary  to  set  up  a 
flux  of  120,000  lines  of  force  in  the  iron  at  a  voltage  of  110. 

no  x  100,000,000 

-  4.44  x  120,000  X  60 
==  344  turns. 

Since  the  input  in  watts  is  1,063.83  at  110  volts,  the  am- 
peres to  flow  in  the  primary  at  full  load  is 

(12)  Watts  =  £7 

1,063.83  =  1107 

1,063.83 
7  =  —  —  —  —      9.67  amperes. 

Assuming  1,000  circular  mils  per  ampere,  the  size  of  the 
wire  necessary  to  carry  10  amperes  can  be  obtained  from  Table 
IV.  If  we  look  in  the  column  headed  "Circular  Mils,"  un- 
til we  come  to  the  number  10,381  circular  mils,  and  divide 
this  by  1,000  circular  mils  per  ampere,  we  have  the  number 
10.  Looking  under  the  column  headed  "Gauge  Number,"  we 
find  Xo.  10  wire.  This  means  that  No.  10  copper  wire  will 
carry  10  amperes  without  undue  heating,  allowing  1,000  cir- 
cular mils  per  ampere. 

If  the  numbers  in  the  column  headed  "Circular  Mils"  be 
.divided  by  1,000,  the  resulting  number  is  the  number  of  am- 
peres that  the  wire  opposite  it  will  safely  carry. 

Referring  to  table  No.  V,  we  find  that  No.  10  double  cot- 
ton covered  wire  has  8.51  turns  per  inch  of  length  of  helix.  Al- 
lowing l/2  inch  at  each  end  in  order  to  get  the  primary  away 


176  WIRELESS  TELEGRAPHY  AND 

from  the  iron  at  the  ends  of  the  core,  we  have  10  inches  in 
which  to  place  the  primary  winding.  8.51  turns  to  the  inch 
gives 

8.51  X  10  =  85  turns 

per  layer.     Since  there  are  to  be  344  turns,  it  requires 
344/85  =  4  layers. 

The  depth  of  the  winding  is 

4/8.51  X  1  inch  =  .47  inches. 

The  empire  cloth  occupies  about  y^  inch,  and  the  total 
space  occupied  by  the  primary  is 

.25  +  .47  ==  .72  inches, 

or  practically  %  inch.  A  tap  should  be  brought  out  at  the 
end  of  the  second,  third  and  fourth  layer. 

In  order  to  calculate  the  amperes  in  the  primary,  apply 
the  following  formula : 

Watts  input  =  amperes  X  volts 

1,058.2=  1107 
I  =  1,058.2/110  =  9.6  amperes. 

The  amperes  to  flow  in  the  primary  of  the  transformers 
between  100  to  500  watts,  inclusive,  are  calculated  as  follows : 
Take  the  200-watt  as  an  example.  From  the  design. the  200- 
watt  transformer  requires  1,200  turns. 

200  ;=  1107  and  /  =  200/110  =  1.81  amperes. 
1,200  X  1-^1   amperes  gives  2,072  ampere  turns  necessary  to 
drive  the  flux  through  the  iron.     Since  we  are  going  to  use 
but  666  turns,  the  amperes  necessary  to  get  the  same  ampere 
turns  is  as  follows : 

2,072/666  =  3.1  amperes. 

This  works  the  iron  at  a  higher  density  and  it  really  makes 
a  340-watt  transformer  of  it,  worked  at  a  high  density.  Al- 
lowing 1,000  circular  mils  per  ampere,  the  table  shows  us  that 
it  is  necessary  to  use  No.  15  wire  for  this  transformer. 

All  other  transformers  in  the  table,  following  the  500-watt, 


HIGH  FREQUENCY  ELECTRICITY  .  177 

are  calculated  in  the  same  way  as  the  1,000- watt  transformer 
here  calculated. 

In  Table  I,  column  8  is  taken  directly  from  Table  V. 
Column  11  is  derived  from  Fig.  85,  and  column  12  is  computed 
from  columns  8  and  11.  In  the  case  of  the  200-watt  trans- 
former, 

14.68  turns  per  inch  X  ?*/2  ==  111.1  turns 

per  layer.  Column  9  is  formed  by  dividing  column  6  by  col- 
umn 12.  Column  10  is  computed  by  dividing  column  9  by  col- 
umn 8. 

Column  13  is  formed  by  combining  columns  2,  3  and  4  as 
in  Fig.  85.  Column  14  is  found  in  the  same  way  that  it  is 
found  in  designing  the  1,000-watt  transformer.  It  should  be 
nearly  the  same  as  column  13. 

Column  15  is  found  by  multiplying  column  13  by  column 
20.  Column  16  is  worked  out  from  Fig.  85.  Column  17  is 
found  as  follows :  Take  the  1,000-watt  as  an  example.  The  iron 
is  2  inches  on  each  side.  To  this  add  y2  inch  for  insulation, 
i.e.,  y\.  inch  on  each  side.  This  gives  2.5  inches ;  4  X  2.5  inches 
gives  10  inches  as  the  distance  around  the  insulated  core.  This 
then  is  the  length  of  the  turns  first  put  on. 

The  winding  has  a  depth  of  .47  inches.  Take  twice  this 
or  .94  and  add  "it  to  the  2.5  inches  in  order  to  get  the  length  of 
one  side  of  the  fourth  layer.  This  gives  3.44  inches.  Multiply 
this  by  4  in  order  to  get  the  length  of  an  outside  turn.  It  is 
13.76  inches.  Add  13.76  inches  and  10  inches  and  divide  by 
2  in  order  to  get  the  average  turn.  This  gives  11.88  inches. 

Multiply  by  the  number  of  turns  and  ^divide  by  12  to  get 
the  length  of  the  wire  in  feet  for  the  primary.  It  is  340  feet. 

From  Table  IV  obtain  the  pounds  per  foot  of  No.  10  wire. 
It  is  .0331.  Multiply  this  by  344.  It  results  in  10.7  pounds  of 
No.  10  D.C.C.  wire.  This  is  given  in  column  18.  Column  19 
is  assumed.  Column  20  is  taken  from  Table  IV. 

Table  II  gives  the  data  for  the  secondary.  From  column 
2  it  is  seen  that  we  are  to  use  No.  32  wire  in  the  secondary. 
Column  3  shows  the  thickness  of  the  pies  or  coils,  and  column 
4  gives  the  diameter  of  the  annular  ring  of  the  coils. 


178  WIRELESS  TELEGRAPHY  AND 

The  free  space  between  the  primary  and  secondary  is  4*4 
inches  (see  Fig.  85).  The  primary  occupies  .72  inches.  The 
secondary  insulation  occupies  *4  inch.  Allow  Y^  inch  free 
space  between  the  inside  turns  of  the  coil  and  the  insulation  on 
the  iron.  The  coils  are  2  inches  in  diameter  across  the  wind- 
ings. Adding  all.  these  gives,  .72  -f  .25  -f  .25  +  2.00  =  3.22 
inches  occupied  by  the  primary  and  secondary.  Subtracting 
this  from  4^  inches  leaves  1.03  inches  between  primary  and 
secondary. 

Allow  Y%  inch  between  each  coil  for  insulation.  Each 
coil  then  occupies  l/%  -f-  y^  inch  or  ^  inch. 

Allow  an  inch  between  the  ends  of  the  iron  core  and  the 
ends  of  the  secondary  coils.  This  leaves  9  inches  of  winding 
space.  This  gives  9  X  8/3  =  24  coils.  Column  7  is  found 
in  this  way. 

The  cross  section  of  a  coil  is  the  product  of  columns  3  and 
4.  This  is  14  X  2  —  ^  square  inches.  From  Table  V,  No. 
32  D.C.C.  is  found  to  have  4,027  turns  per  square  inch  of 
cross  section.  y2  X  4,027  —  2,013  turns  in  a  coil,  where  the 
turns  are  put  on  carefully  side  by  side.  Since  we  are  to  wind 
on  the  turns  rather  rapidly  in  the  lathe,  1/5  must  be  sub- 
tracted for  rapid  winding.  Divide  2,013  by  5.  It  gives  402. 
Subtract  this  from  2,013,  and  it  leaves  1,611  turns  in  each  coil 
of  the  secondary.  This  is  found  in  column  6.  Column  8 
is  taken  from  Table  V. 

Since  there  are  to  be  24  coils,  24  X  1,611  gives  38,664  as 
the  number  of  turns  in  the  secondary.  From  the  formula 
Tp:Ts::Ep:Es,  the  voltage  in  the  secondary  is  computed. 

In  this  case 

344:38,664::  110  :Ry 

110  X  38,664 
and  Es  =—     C\         —  =  12,363 


Column  10  is  calculated  in  this  manner.  Columns  15,  16, 
17,  18,  19  and  20  are  calculated  in  the  same  manner,  for  the 
turns  designated.  If  higher  voltages  are  desired  with  all  the 
turns  in,  the  coils  can  be  made  larger  in  diameter,  in  which 


HIGH  FREQUENCY  ELECTRICITY  179 

case  the  iron  core  must  be  made  wider  or  the  core  can  be  made 
longer  and  more  coils  can  be  put  on. 

By  cutting  out  turns  in  the  primary,  the  voltage  can  be 
raised  as  shown  in  columns  15  to  20,  already  mentioned. 

The  transformer  can  be  operated  on  all  these  taps,  pro- 
vided a  water  rheostat  is  used  in  the  primary  to  cut  back  the 
current.  Column  5  gives  the  size  for  the  opening  in  the  coil. 

It  is  determined  as  follows :  The  iron  is  2  inches  on  a  side. 
Since  the  empire  cloth  is  ^  mcn  thick,  it  will  add  2  X  /4  °r 
]/2  inch  to  the  opening.  This  makes  2.5  inch  opening. 

To  calculate  the  amount  of  wire,  proceed  as  follows :  2.5 
inches  taken  from  column  5  multiplied  by  4  gives  10  inches  as 
the  length  of  one  turn  next  the  core.  Since  the  coil  is  2  inches 
across,  the  outside  dimension  is  4  inches  longer,  hence  4  -f-  2.5 
gives  6.5  inches  as  the  length  of  one  side  of  the  outside  turns. 
This  multiplied  by  .4  gives  26  inches  as  the  length  of  the 
outside*  turn.  Add  26  and  10  and  divide  by  2  for  the  average 
turn.  This  is  18  inches.  Divide  by  12  in  order  to  express  it  in 
feet.  It  is  1.5  feet.  Multiplying  1.5  by  38,664,  gives  55,996  feet 
of  wire  in  the  secondary.  This  is  found  in  column  11.  Col- 
umn 12  is  found  by  multiplying  the  pounds  per  foot  taken 
from  Table  IV  by  the  number  of  feet. 


180 


WIRELESS  TELEGRAPHY  AND 


Plate  I.     A.  Frederick  Collins  transmitting  and  receiving^wireless  tele- 
phone messages  between   Newark,   N.  J.,   and   Philadelphia, 
.  September,  1908 


HIGH  FREQUENCY  ELECTRICITY  181 


WIRELESS  TELEPHONY 

by 

William   Dubilier 
Chief  Electrician  of  the  Collins  Wireless  Telephone  Company 

INTRODUCTION 

Up  to  the  present  time  every  known  wireless  telegraph  system 
has  been  utilizing  damped  electric  oscillations.  It  was  not  until  lately 
that  some  of  our  greatest  scientists  and  inventors  have  expressed  their 
belief  that  by  such  means  the  greatest  drawback  that  we  have  to  con- 
tend with,  that  is,  imperfect  tuning,  will  never  be  eliminated  and  per- 
fect tuning  will  only  be  possible  by  using  undamped  or  persistent 
electric  oscillations. 

Since  the  possibility  of  the  wireless  telephone  depends  entirely 
upon  the  production  of  such  oscillations  and  suitable  means  for  vary- 
ing them,  we  may  predict  that  in  the  near  future  the  wireless  tele- 
phone will  not  only  progress  far  ahead  of  the  wireless  telegraph,  but 
take  its  place.  For  it  can  be  used  either  for  wireless  telegraphy  or 
wireless  telephony.  It  also  does  away  with  the  spark. 

WM.  DUBILIER. 

There  are  a  number  of  different  ways  of  producing  elec- 
tric oscillations,  the  best  known  being  an  induction  coil  or 
transformer,  and  the  one  that  is  about  the  least  known  being 
an  ordinary  arc  lamp,  energized  by  a  direct  current.  The 
difference  between  the  two  being  that  in  the  former  they  are 
damped  and  in  the  latter  they  are  undamped  or  continuous. 

Undamped  or  persistent  oscillations  are  high  frequency 
alternating  currents,  just  as  are  the  alternating  currents  used 
for  electric  lighting  and  the  transmission  of  po\ver,  the  only 
difference  being  that  the  frequency  of  one  is  anywhere  from 
1,000  to  100,000  times  greater  than  the  other. 

There  are  several  methods  used  for  producing  such  cur- 
rents. One  is  by  the  use  of  the  high  frequency  alternator,  the 
invention  of  wdiich  dates  back  to  1889,  when  arc  lighting  by 
alternating  currents  became  popular,  the  sound  of  which  they 
tried  to  eliminate  by  increasing  the  frequency. 

Nikola  Tesla  constructed  a  machine  which  consisted  of  a 
fixed  ring-shaped  field  magnet  with  magnetic  poles  inwards, 


182  WIRELESS  TELEGRAPHY  AND 

and  a  rotating  armature  in  the  form  of  a  fly  wheel.  The  mag- 
net had  400  radial  poles  in  the  circumference  and  400  coils  on 
the  armature.  When  driven  at  a  speed  of  3,000  revolutions  per 
minute  or  50  per  second,  it  produced  an  alternating  current  'of 
10,000  cycles.  The  output  of  this  was  limited  to  a  small 
amount  of  energy,  probably  not  more  than  y2  kilowatt.  It 
was  dangerous,  however,  to  run  such  a  machine. 

The  Westinghouse  Co.  has  built  for  Mr.  G.  B.  Famme  an 
alternator  having  a  2-kilowatt  capacity  at  a  frequency  of  10,000. 
It  is  of  an  induction  type  and  has  200  polar  projections. 

In  all  these  machines  it  is  customary  to  make  the  field 
magnet  the  revolving  part,  the  armature  being  stationary. 

Duddell  succeeded  in  building  a  machine  of  the  induction 
type  which,  at  a  speed  of  30,000  revolutions  per  minute,  gave  a 
current  of  one  ampere  and  a  frequency  of  15,000  per  second  at 
40  volts. 

There  is  claimed  to  be  built  a  machine  possible  to  create 
an  'alternating  current  having  a  frequency  of  100,000,  when 
the  disc  is  driven  at  a  speed  of  600  revolutions  per  second, 
the  output  being  only  0.1  of  an  ampere  at  2  volts. 

R.  A.  Fessenden  claims  to  have  constructed  a  machine 
with  a  frequency  of  60,000,  with  an  output  of  not  more  than 
200  watts,  at  a  speed  of  10,000  revolutions  per  minute.  Al- 
though this  machine  was  sufficient  for  experimental  purposes, 
it  was  far  from  being  practical  for  wireless,  the  output  being 
too  small  and  the  machine  being  too  dangerous  to  run. 

It  is  said,  on  one  occasion,  while  one  of  these  machines 
was  going  at  its  normal  speed,  that  a  magnet  flew  from  the 
field,  clear  through  a  two-foot  brick  wall  and  250  feet  out  into 
the  field.  The  efficiency  being  very  low,  the  machine  danger- 
ous, and  the  output  small,  tend  to  make  the  high  frequency 
alternator  very  impractical  and  useless  at  its  present  stage. 

From  the  experience  so  far  received  by  the  scientific  world, 
we  may  conclude :  First,  that  an  attempt  to  run  alternators  at 
high  speeds,  say  above  5,000  revolutions  per  minute,  involves 
the  loss  of  considerable  energy  due  to  air  friction  and  churn- 
ing, hence  it  cannot  have  a  high  efficiency;  second,  that  the 
size  of  the  armature  and  its  peripheral  velocity  has  its  practical 


HIGH  FREQUENCY  ELECTRICITY 


183 


limitations;  third,  in  using  an  induction  type  of  motor,  it  labors 
under  the  disadvantage  that  an  attempt  to  take  a  current  out 
of  the  machine  generally  results  in  a  large  drop  in  the  terminal 
potential  difference.  It  is,  therefore,  exceedingly  hard  to  com- 
bine in  one  alternator  the  properties  of  high  frequency,  high 
power  and  a  large  power  output.  Such  machines  are  not  as 
yet  commercial  articles,  hence  the  alternating  method  of  pro- 
ducing undamped  oscillations  has  up  to  the  present  only  come 
into  limited  use,  although  there  is  a  possibility  of  it  being 
improved. 

The  Arc  Method  of  Producing  Undamped  Oscillations 

Up  to  the  time  Duddell  described  his  singing  arc,  many 
inventors  struggled  to  combine  an  arc  lamp  with  a  capacity 
and  inductance  for  producing  oscillations,  but  met  with  little 
success.  As  early  back  as  1840,  Grove  describes  an  arc  lamp 
burning  in  hydrogen  and  its  effects.  In  1875  de  La  Rue  and 
Hugo  Miller  used  an  arc  in  hydrogen  in  experimenting  on  some 
vacuum  tubes,  and  in  1892  Elihu  Thompson  patented  the  fol- 
lowing method  for  transforming  an  alternating  current  in  an 
alternator : 

In  Fig.  i,  G  is  a  direct  current  generator  in  the  same  cir« 
cuit  with  a  very  high  inductance  R,  a  spark  gap,  and  two  metal 
balls  >S\  These  balls  are  connected  in  another  circuit,  consist- 
ing of  a  condenser  C  and  an  inductance  L  in  series.  When  the 
spark  balls  are  brought  in  contact,  a  current  is  drawn  through 
the  inductance  L.  If  the  balls  are  separated,  the  condenser 
will  become  charged  by  the  difference  of  potential  created,  and 


Fig.  1 

G,  B.C.  generator;  R,  inductive  resistance;  S,  arc  gap;  C,  condenser; 

L,  inductance. 


184  WIRELESS  TELEGRAPHY  AND 

when  fully  charged  it  discharges  across  the  gap.  Thompson 
claimed  to  obtain  oscillations  of  30,000  per  second,  but  no 
proof  was  given  in  his  specifications  that  these  were  not  inter- 
mittant.  Although  this  was  quite  theoretical,  it  shows  that 
he  was  trying  to  find  means  for  producing  undamped  oscilla- 
tions. 

About  the  same  time  Firth  and  Rodgers  gave  out  the 
statement  that  the  current  through  an  arc  was  oscillating  and 
that  they. had  succeeded  in  converting  3%  of  the  continuous 
current  into  an  oscillating  one. 

It  was  not  until  Duddell  made  his  discovery  in  1900  that 
the  matter  was  seriously  thought  of.  He  described  some  of 
his  observations  made  before  the  London  Institute  of  Electric 
Engineers  on  the  solid  carbon  arc  lamp,  having  a  capacity 
and  inductance  shunted  across  it,  showing  its  oscillating  na- 
ture. In  his  circuit  he  used  a  direct  current  generator  of  3.5 
amperes  and  a  potential  difference  of  42  volts.  Around  the 
arc  he  shunted  a  capacity  of  about  3  microfarads  in  series 
with  an  inductance  of  5  millihenries.  Under  such  conditions 
the  arc  gave  out  a  musical  tone,  the  pitch  of  which  depended 
upon  the  capacity  and  inductance.  Since  the  musical  tone  is 
due  to  the  rapid  change  in  the  arc,  a  very  important  factor 
arises  which  may  open  the  way  later  for  a  new  method  of  pro- 
ducing undamped  oscillation,  and  the  author,  working  on  this 
theory,  has  been  quite  successful.  An  important  factor  must 
be  taken  into  consideration  in  the  Duddell  arc.  The  inductance 
in  the  direct  current  circuit  must  have  a  high-  resistance  and 
inductance  as  compared  with  the  resistance  or  inductance  in 
the  oscillating  circuit.  If  we  draw  the  characteristic  curve  of 
a  D.C.  arc,  we  will  find  that  it  does  not  quite  agree  with  Ohm's 
law;  that  is,  it  is  not  a  straight  line  as  the  case  would  be  with 
a  metallic  conducting  circuit. 

If  we  take  observations  with  a  voltmeter  and  ammeter  on 
a  solid  carbon  direct  current  arc,  for  various  constants  of  the 
arc,  using  the  potential  difference  in  volts  as  the  ordinate,  and 
the  current  in  amperes  as  abscissa,  we  will  find  a  curve  that  is 
concave  upward  and  as  the  current  increases  it  slopes  down- 
ward; it  is  therefore  a  curve  that  slopes  in  the  opposite  direc- 


HIGH  FREQUENCY  ELECTRICITY 


185 


tion'  to  the  curves  that  obey  Ohm's  law.  All  this  phenomena 
has  been  investigated  by  Messrs.  Ayrton,  Upson  and  others, 
and  the  conclusion  is  that  in  all  cases,  whether  between  carbon 
and  carbon,  or  carbon  and  metal,  or  these  with  gases,  the 
curves  slope  downward,  showing  that  as  we  increase  the  cur- 
rent through  the  arc  the  potential  difference  decreases. 

The  action  of  the  capacity  and  inductance  on  the  arc  may 
be*as  follows : 


Fig.  2.     Dudclell's  circuit. 

G,  D.C.  generator;  R,  inductive  resistance;  S,  arc  gap;   C,  condenser; 

L,  inductance. 

In  shunting  the  capacity  C  and  inductance  L  across  an 
arc  (see  Fig.  2}  that  is  burning  steadily,  the  capacity  instantly 
takes  upon  itself  a  charge  and  the  current  through  the  arcs 
is  at  the  same  time  diminished,  the  potential  difference  there- 
fore increases  across  the  arc  and  this  tends  further  to  charge 
the  condenser.  This  reacts  on  the  arc  and  still  further  in- 
creases its  current,  which  in  turn  lowers  the  potential  differ- 
ence. 

Since  it  discharges  through  an  inductance  L,  it  not  only 
fully  discharges  but  becomes  charged  in  the  opposite  direc- 
tion, just  as  a  pendulum,  when  pulled  to  one  side  and  let  go, 
will  not  only  go  back  to  its  original  position,  but  go  far  beyond 
it  in  the  opposite  direction. 

When  in  this  condition,  it  is  ready  to  repeat  the  operation 
with  more  vigor  than  before,  and  so,  persistent  and  undamped 
oscillations  are  set  up  by  the  condenser  charging  and  discharg- 
ing- 

Suppose  in  swinging  the  pendulum,  we  apply  enough  force 


186 


WIRELESS  TELEGRAPHY  AND 


on  each  swing  to  make  up  for  the  friction  and  other  losses 
and  make  it  come  back  to  the  same  position  all  the  time. 
This  can  be  accomplished  only  when  we  apply  the  force  just 
about  the  time  it  starts  to  swing  in  the  opposite  direction, 
since  it  has  its  own  time  period  of  oscillation,  depending  upon 
the  length.  Now  if  we  should  strike  it  before  it  starts  to 
swing  back,  we  will  have  two  forces  in  the  opposite  direction 
applied  to  the  same  points  and  they  will  have  a  tendency  ^to 
neutralize  each  other. 

The  same  applies  to  the  oscillating  circuit.  If  the  capacity 
and  inductance,  each  having  its  own  natural  time  period  of 
oscillation  (into  which  part* of  the  direct  current  is  converted), 
are  not  in  resonance,  that  is,  if  the  capacity  does  not  fit  the 
inductance,  wre  will  have  very  weak  oscillations,  one  counter- 
acting the  other. 

Poulson's  Improvements 

In  1903  the  Danish  physicist,  Poulson,  formed  an  arc  be- 
tween a  water  cooled  metallic  electrode  ^  and  a  solid  carbon 
Si  (Fig.  j),  the  chief  improvement  being,  however,  the  fact 
that  he  burned  his  arc  in  a  medium  of  coal  gas  and  later  used 
alcohol.  With  this  arrangement  he  succeeded  in  obtaining 
much  more  forceful  oscillations  than  were  heretofore  known. 
The  frequency  varied  from  500,000  to  1,000,000  cycles.  When 
the  machine  was  operated,  a  great  amount  of  heat  was  evolved, 
and  although  the  water  cooled  the  copper  rod  to  some  extent, 


Fig.  3.     Poulson's  water-cooled  arc. 

G,  B.C.  generator;  R,  inductive  resistance;  S,  arc  gap;  C,  condenser; 

L,  inductance. 

Si,    carbon    electrode;    S,    copper    electrode;    Wi,    water    pipe    outlet: 
W,   water  pipe  inlet;   L,   Li,  inductive   coupling. 


HIGH  FREQUENCY  ELECTRICITY  187 

one  .may  readily  understand  how  inconvenient  such  an  arrange- 
ment is.  However,  the  advantages  gained  by  the  fact  that 
undamped  oscillations  were  obtained,  which  as  stated  in  the 
beginning  makes  tuning  possible,  induced  him  to  proceed  at 
once  and  apply  his  machine  to  the  practice  of  wireless  teleg- 
raphy. 

Now  in  summing  up  the  work  done  with  the  arc,  H. 
Simon  and  Fleming  came  to  the.  conclusion,  that  in  order  to 
obtain  strong  undamped  oscillations  ,  one  must  have  an  arti- 
ficially cooled  electrode  for  positive  process,  and  this,  I  think, 
has  been  solved  by  Mr.  A.  Frederick  Collins.  Since  1900  he 
has  been  working  on  the  combination  of  an  arc  lamp  and  trans- 
mitter for  wireless  telephonic  work,  thus  being  practically 
ahead  of  all  other  physicists. 

At  the  time  Duddell  conceived  of  the  musical  arc,  he  had 
no  idea  of  its  being  used  in  connection  with  a  transmitter  for 
wireless  telephony.  A  description  of  this  was  given  in  the 
Scientific  American  of  July  18,  1902,  showing  that  he  was  the 
first  scientist  to  apply  an  arc  lamp  for  wireless  telephony.  The 
publication  of  Poulson's  experiments,  showing  that  the  cooling 
of  the  arc  lamp  electrodes  was  the  cause  of  powerful  oscilla- 
tions, led  Mr.  Collins  to  deeply  investigate  and  evolve  a  perfect 
system  of  wireless  telephony. 

In  the  Poulson  method  of  producing  oscillations,  if  the  arc 
was  left  burning  for  some  time,  the  machine  and  its  parts 
\yould  gradually  heat  up,  and  the  water  in  the  tank  would  be- 
come warm.  It  was  not  safe  to  connect  the  water  cooled  elec- 
trode to  a  water  pipe,  since  this  would  ground  the  machine 
and  interfere  with  its  operation.  The  question  of  cooling  was 
therefore  an  important  one,  as  pointed  out  before.  Mr.  Collins 
then  produced  his  revolving  arc,  lamp,  in  which  the  electrodes 
were  revolved  by  a  small  motor  or  clockwork.  This  at  once 
eliminated  all  troubles  due  to  heating,  also  to  getting  rid  of  a 
large  amount  of  energy  dissipated  as  heat. 

The  first  application  of  the  direct  current  arc  to  wireless 
telephony  was  made  by  Collins  in  1902,  and  since  that  time  he 
has  devised  many  a  form  of  arc  lamp  for  the  production  of 


188 


WIRELESS  TELEGRAPHY  AND 


sustained  oscillations,  one  of  which  is  shown  photographically 
in  Fig.  4,  top  view  Fig.  5  and  in  cross  section  in  Fig.  6. 


Fig.  4.     The   Collins  rotating  oscillation  arc. 

In  1903,  when  experimenting  with  the  musical  arc,  Potil- 
son  found  that  more  intense  oscillations  were  obtained,  if  the 
arc  is  formed  between  a  cool  metallic  electrode  and  a  solid 
carbon. 

Collins  has  ascertained  that  a  greater  percentage  of  direct 
current  is  converted  into  high  frequency  oscillations,  providing 
carbons  are  used,  and  one  or  both  are  kept  at  a  low  tempera- 
ture. In  order  to  accomplish  this  in  practice,  he  employs  a 
pair  of  carbon  or  graphite  disks  as  the  anode  and  the  cathode. 
These  disk's  are  mounted  on  parallel  spindles  so  that  they 
are  in  the  same  plane  and  are  connected  by  means  of  beveled 
gears  to  an  insulated  shaft. 


HIGH  FREQUENCY  ELECTRICITY  189s 

The  disks  are  insulated  from  each  other  by  fiber  bush- 
ings inserted  in  the  gearings,  the  casing  forming  one  of  the 
connections,  w^hile  the  insulated  bearing  in  the  bottom  of  the 
casing  forms  the  other.  The  gearing  is  so  arranged  that  car- 
bon disks  are  rotated  in  opposite  directions,  the  power  being 
furnished  by  a  ^  horse-power  motor.  One  of  the  bearings  in 
the  shaft  is  mounted  in  a  keyed  sleeve  which  permits  the 
spindle  carrying  one  of  the  disks  to  be  moved  .toward  or  away 
from  the  opposite  disk  so  that  the  length  of  the  arc  can  be 
varied  while  the  lamp  is  in  operation.  The  carbon  electrodes 
are  placed  in  a  metal  casing  while  the  rotating  mechanism  is 
attached  to  the  bottom  casing. 


Fig.  5.     Plan  view  of  the  Collins  arc. 

The  casing  is  supported  between  the  poles  of  an  electro- 
magnet, and  through  the  ends  of  the  poles  and  at  right  angles 
to  them,  are  polar  rods  of  soft  iron  which  are  threaded.  These 
are  screwed  through  the  extremities  of  the  magnet  and  at 
right  angles  to  the  arc.  The  ends  terminating  in  the  casing 
are  pointed,  while  those  projecting  outside  have  disks  of  hard 
rubber  so  that  they  may  be  adjusted  in  positions  to  the  arc. 
The  magnet  coils  are  placed  in  each  of  the  leads  of  the  supply 
circuit,  and  serve  as  well  to  choke  back  the  oscillations  from 
reaching  the  generator.  The  casing  is  supported  between  the 
poles  of  the  magnet  and  the  magnet  in  turn  is  held  in  position 
by  an  iron  base. 


190 


WIRELESS  TELEGRAPHY  AND 


The  magnets  provide  a  strong  magnetic  field  in  which  the 
arc  burns  and  so  increases  the  resistance  between  the  carbons 
and  hence  raises  the  voltage.  The  adjustable  poles  of  the  mag- 
net are  used  primarily  to  blow  back  and  keep  the  arc  between 
the  carbons  where  the  distance  is  shortest.  Were  this  not 
done,  the  arc  would  follow  the  revolving  carbons  until  broken. 
The  arc  has  been  burned  in  different  gases,  under  pressure  and 
in  vacuum. 


u  u 

Fig.  6.    Side  elevation  of  the  Collins  arc. 

In  experimenting  with  this  arc  with  different  gases,  the 
author  has  discovered  that  certain  conditions  existed  in  the  arc 
chamber  heretofore  unknown,  one  being  that  certain  gases  un- 
der certain  conditions  do  not  burn  continuously  but  explode 
with  a  very  great  rapidity.  It  was  on  one  occasion  when  using 
this  gas  in  connection  with  the  arc  that  undamped  oscillations 
were  obtained  in  the  aerial  system  which  indicated  two  times 
as  much  current  on  a  hot  wire  ammeter  than  was  previously 
obtained. 

Upon  further  investigation  more  detailed  specifications 
will  be  made  public  in  the  near  future. 

The  rotating  oscillation  arc  eliminates  the  disadvantageous 
features  of  the  stationary  arc  in  that  a  constantly  fresh  and 


HIGH  FREQUENCY  ELECTRICITY  191 

cool  surface  is  presented  to  the  arc,  and  in  that  it  prevents 
the  burning  away  of  the  electrodes  which  gives  rise  to  un- 
toward variations  in  the  frequency  of  the  oscillations,  and 
finally  in  that  the  optumum  length  of  the  arc,  namely,  at  the 
length  when  the  frequency  of  the  oscillations  is  the  greatest, 
may  be  maintained  for  long  periods  of  time,  which  is  quite 
impossible  when  the  carbons  are  stationary. 


Fig.  7.     Adjustable  condenser. 

Across  this  arc  is  connected  an  oscillation  circuit  having 
a  variable  condenser  (see  Fig.  7)  consisting  of  metal  plates 
placed  above  one  another  in  a  large  tank  of  insulating  white 
paraffine  oil.  One  set  of  plates  is  fixed  on  a  shaft  so  that  it 
can  be  revolved  and  brought  between  the  other  set,  so  that 
any  variation  of  capacity  can  be  obtained.  It  is  upon  this 
condenser  that  free  oscillations  of  considerable  force,  so  to 


192  WIRELESS  TELEGRAPHY  AND 

speak,  depend.  *  The  variable  inductance  included  in  this  cir- 
cuit is  a  single  helix  of  bare  wire,  which  can  also  be  varied 
so  that  any  combination  of  inductance  and  capacity  can.  be 
obtained.  There  is,  however,  one  important  point  to  bear  in 
mind,  and  that  is  the  capacity  must  be  of  a  small  value  as  com- 
pared with  the  inductance  and  adjusted  so  that  a  frequency 
may  be  obtained  anywhere  from  100,000  to  1,000,000  cycles 
per  second. 

In  one  test  made  by  Mr.  Collins  between  Newark  and 
Philadelphia,  a  distance  of  ninety  miles,  described  in  the  Sci- 
entific American  of  September  19,  1909,  a  revolving  arc  lamp 
energized  by  a  current  of  8  amperes  at  500  volts  was  set  in 
operation  in  connection  with  a  resonance  tube  used  for  tuning. 
This  consists  of  an  exhausted  glass  tube  13  inches  in  length 
and  \Y\  inches  in  diameter.  Sealed  in  the  ends  are  platinum 
wires  1/1C  inch  in  diameter,  and  these  extend  longitudinally 
through  the  center  of  the  tube  until  the  ends  almost  touch  each 
other.  The  outside  terminals  are  connected  in  shunt  with  the 
induction  coil.  Now,  when  the  first  feeble  oscillations  begin 
to  surge  in  the  closed  circuit,  one  or  the  other  will  glow,  or 
both  of  the  free  ends  of  the  enclosed  wires  will  glow,  depending 
upon  the  oscillatory  nature  of  the  current.  As  the  current 
strength  of  the  oscillations  increases,  the  glow  light  extends 
farther  and  farther  toward  the  ends  of  the  tube,  always  keeping 
close  to  the  oppositely  disposed  wires. 

The  length  of  the  glow  on  the  wires  is  proportional  to 
the  current  strength,  and  thus  the  tube  may  also  be  used  as  a 
measuring  apparatus  instead  of  the  milliammeter  usually  em- 
ployed. The  characteristics  of  the  oscillations  can  also  be 
easily  observed ;  for  if  they  are  positive  the  light  will  appear 
almost  entirely  on  the  end  of  one  of  the  wires,  and  if  the 
current  is  reversed,  on  the  opposite  end ;  while  if  the  current 
is  oscillating  with  equal  electromotive  forces,  the  light  will 
have  the  same  degree  of  intensity  on  both  wires.  By  means 
of  a  revolving  mirror  the  oscillations  may  be  segregated,  and 
it  is  then  easy  to  see  whether  they  are  periodic  or  continuous,", 
and  if  the  latter,  to  analyze  the  wave  form  of  the  spoken  words. 

Upon   the   Land   Title   Building,   Philadelphia,   Pa.,   were 


HIGH  FREQUENCY  ELECTRICITY 


193 


raised  three  kites  in  tandem  to  which  the  aerial  was  connected. 
The  aerial  at  Newark  consisted  of  1,500  feet  of  phosphor  bronze 
wire.  By  means  of  a  reel  at  Philadelphia,  about  the  same 
length  of  aluminum  wire  was  let  out,  which  made  the  attuning 
of  both  instruments  quite  easy.  Plate  I  shows  Mr.  Collins  at 
the  time  talking  to  Philadelphia,  where  the  speech  was  re- 
ceived quite  audibly  and  clearly. 

Although  very  good  results  were  obtained  by  him  a  short 
time  previous  between  his  Newark  laboratory  and  the  Singer 
Building,  New  York,  a  distance,  of  9  miles,  and  between  New- 
ark and  Rockland  Lake,  a  distance  of  about  40  miles,  the 


Fig.  8.     The   Elements  of  the   Collins  wireless  telephone   system  and 
their  electrical  relation  to  one  another. 

Philadelphia  test  was  the  greatest  distance  ever  made  on  this 
side  of  the  Atlantic  Ocean.  Fig.  8  shows  a  wiring  diagram 
of  the  apparatus. 

Controlling  the  Waves  by  Means  of  a  Telephone  Transmitter 

Many  different  combinations  and  arrangements  have  been 
tried  in  connecting  up  the  transmitter  with  the  oscillating  cir- 
cuit, but  in  all  my  experiments  with  the  wireless  telephone,  I 
have  found  it  most  practical,  in  fact  the  only  possible  way  to 
get  good  results,  to  work  the  transmitter  on  an  independent 
circuit  of  its  own  and  connect  that  inductively  to  the  arc,  or 
superimpose  it  upon  the  direct  current  supplied  to  the  arc. 

Many   experimenters   claim    results   with   the   transmitter 


194  WIRELESS  TELEGRAPHY  AND 

connected  to  the  ground  circuit.  Upon  experiment,  this  will 
be  found  to  be  almost  impossible,  as  the  high  frequency  oscil- 
lations of  three  or  four  amperes  would  arc  the  carbon  and  burn 
it  out. 

In  the  last  distance  tests  made,  the  terminals  of  a  small 
transformer  coil  were  shunted  across  the  arc,  but  a  condenser 
of  a  large  capacity  is  interposed  to  check  the  high  voltage 
direct  current  from  flowing  through  it.  The  primary  of  the 
transformer  was  connected  in  series  with  a  25-volt  generator 
and  a  telephone  transmitter,  as  shown  in  the  wiring  diagram. 
Now  when  the  arc  is  set  in  operation,  a  slight  change  in  its 
resistance  would  vary  the  oscillating  circuit  and  hence  change 
the  amplitude  of  the  waves  sent  out.  Upon  speaking  into  the 
transmitter,  the  current  through  the  primary  of  the  trans- 
former produces  an  alternating  current  at  the  ends  of  the 
secondary  circuit  on  the  direct  current  of  the  arc,  and  changes 
its  resistance,  which  in  turn  varies  the  oscillating  circuit. 

The  amplitude  of  the  electric  waves  changes  in  the  same 
manner  and  is  proportional  to  the  change  of  air  pressure 
against  the  diaphragm  and  the  current  through  the  trans- 
mitter. The  transmitter  may  also  be  inductively  connected  to 
the  inductance  or  to  some  plates  of  the  condenser. 

Marjorana's  Liquid  Transmitter 

Marjorana  has  been  using  the  intermittent  discharge  of  a 
condenser  by  increasing  its  rapidity  and  he  has  produced  dis- 
charges at  the  rate  of  10,000  per  second ;  these  discharges  in 
turn  consist  of  a  train  of  oscillations.  This  he  has  done  by  the 
use  of  a  very  short  spark  gap,  a  high  inductance  in  series  with 
the  electromotive  force  and  large  impressed  voltage.  In  his 
transmitter  he  utilizes  the  action  of  a  liquid  flowing  from  a 
tube,  which  is  sensitive  to  sound  vibrations. 

A  fine  stream  of  liquid  flows  out  at  one  end,  and,  when 
there  is  no  sound,  a  straight  and  unbroken  column  of  water 
passes  between  two  conductors  to  which  the  instruments  are 
connected.  When  a  sound  is  made,  the  water  column  is  found 
to  contract  in  certain  places  which  forms  a  wavy  column. 


HIGH   FREQUENCY  ELECTRICITY 


195 


Contact  is  made  by  the  liquid  between  the  two  terminals, 
and  when  the  liquid  flows  unevenly,  we  have  a  varying  resist- 
ance between  the  two  terminals. 


Fig.   9.      Collins    thermo-electric    detector    dissected. 
Collins  long  distance  wireless  telephone  receiver. 


Receiving  Instruments 

The  receiving  instruments  used  for  wireless  telephony 
contain  certain  forms  of  detectors,  as  all  wireless  telegraph 
receivers  are  not  suitable  for  wireless  telephony.  For  example, 
detectors  of  the  coherer  or  imperfect  contact  type  will  only 
detect  oscillations,  but  do  not  indicate  changes  in  their  am- 
plitude. 

Three  forms  of  detectors  have  been  used  with  much  suc- 
cess, viz. :  The  thermo-electric,  electrolytic,  and  the  ionized 
gas  detector.  Of  these  the  first  seemed  to  work  about  the 
best,  as  a  form  has  been  devised  by  Mr.- Collins  which  elimin- 
ates all  troubles  of  adjusting  after  once  placed  in  position.  It 
is  different  from  all  other  detectors  previously  invented,  and 
the  principle  upon  which  it  works  is  as  follows :  Two  exceed- 
ing fine  wires  of  different  metals,  crossing  at  right  angles,  are 


196 


WIRELESS  TELEGRAPHY  AND 


made  into  a  thermo-couple  and  so  constructed  that  the  con- 
duction losses  are  far  greater  than  the  radiation  losses.  An- 
other wire  made  of  a  very  high  special  resistance  material 
and  which  is  heated  by  the  received  oscillation  surging  in  it, 
is  mounted  on  a  movable  block  just  underneath  the  couple 
and  its  distance  from  it  can  be  regulated  (see  Fig.  10).  \Yhen 
the  received  oscillations  pass  through  this  wire  of  a  very  high 
specific  resistance,  it  heats  up,  which  in  turn  acts  upon  the 
thermo-couple,  the  resulting  electromotive  force  effecting  a 
very  sensitive  receiver  and  producing  the  voice. 

An  improvement  upon  this  detector  was  recently  made 
by  the  author  by  making  use  of  the  wire  which  is  heated  up 
by  oscillations,  as  one  of  the  metals  of  the  thermo-couple.  This 
detector  is  shown  in  a  photograph  of  the  receiving  set  used 
by  Mr.  Collins  in  telephoning  81  miles  between  Newark  and 
Philadelphia.  Fig.  p  is  a  photograph  of  the  complete  receiving 
outfit. 


Fig.    10.      Collins   thermo-electric   detector    dissected. 


HIGH  FREQUENCY  ELECTRICITY  197 


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199 


TABLE  III. 


Lines  of  Force  per   Square   Inch   Cross   Section 


200 


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201 


TABLE  V. 


Single  Cotton   Cover 

Double  Cotton  Cover 

nj 

*» 

sS 

2  .S 

Turns  per 
Linear  Inch 

Turns  per 
Square  Inch 

No. 

03 

Q 

~      VI 

X   5 

03    « 

i<  .= 

Turns  per 
Linear  Inch 

Turns  per 
Square  Inch 

No. 

472.000 

1.80 

3.60 

0000 

478.00 

1.70 

3.21 

0000 

423.600 

2.08 

4.81 

000 

429.00 

2.00 

4.44 

000 

376  .  800 

2.38 

6.29 

00 

384.00 

2.32 

5.98 

00 

336.900 

2.72 

8.22 

0 

342.00 

2.65 

7.80 

0 

301.300 

3.07 

10.37 

1 

307  .  3 

2.99 

9.93 

1 

269.600 

3.48 

13.45 

2 

275  .  6 

3.36 

12.54 

2 

241.400 

4.00 

17.33 

3 

247.4 

3..  80 

16.04 

3 

216.300 

4.52 

22.70 

4 

226.4 

4.28 

20  .  35 

4 

193.900 

5.05 

27.22 

5 

207.9 

4.83 

25.92 

5 

172.000 

5.60 

34.84 

6 

189.0 

5.44 

32  .  45 

6 

154.300 

6.23 

42.12 

7 

173.3 

6.08 

41.07 

7 

137.500 

6.94 

53.51 

8 

157.5 

6.80 

51.38 

8 

122.400 

7.68 

65.53 

9 

142.5 

7.64 

64.96 

9 

117.900 

8.55 

81.22 

10 

127.9 

8.51 

80.47        10 

96  .  740 

9.60 

102.40 

11 

112.7 

9.58 

101  .97        11 

86.810 

10.80 

129.60 

12 

94.8 

10.62 

125.30        12 

77.960 

12.06 

161.60 

13 

80.96 

11.88 

156.80 

13 

70.080 

13.45 

201.00 

14 

73  08 

13.10 

190  .  70 

14 

63.070 

14.90 

246  .  60 

15 

66.07 

14.68 

239.40 

15 

56  .820 

16.60 

306.10 

16 

59.82 

16.35 

300.00 

16 

51.260 

18.20 

368.10 

17 

54.26 

18.08 

363.20 

17 

46  .300 

20.20 

448.00 

18 

49.30 

19.90 

440.00 

18 

41.840 

22.60 

567.10 

19 

44.89 

21.83 

528.50 

19 

37.960 

25.30 

763.00 

20 

40.96 

23.91 

634  .  80 

120 

34.460 

28.60 

908.80 

21 

37.40 

26.20 

762  .  70 

21 

31  .350 

31.00 

1065.00 

22 

29.12 

28.58 

907.00 

22 

28.570 

34.30 

1307.00 

23 

30.60 

31  .  12 

1075.00 

23 

26.100 

37.70 

1579.00 

24 

28.10 

33  .  60 

1254.00 

24 

23  .900 

41.50 

1914.00 

25 

25.90 

36.20 

1456.00 

25 

21  .940 

45.30 

2280.00 

26 

23.94 

39.90 

1770.00 

26 

20  .200 

49  .  40 

2711.00 

27 

22.20 

42.60 

2016.00 

27 

18.640 

54.00 

3240.00 

28 

20.64 

45  .  50 

2300.00 

28 

17.260 

58.80 

3841.00 

29 

19.36 

48.00 

2560.00 

29 

16.030 

64.40 

4608.00 

30 

18.03 

57.10 

2901.00 

30 

14  .930 

69.00 

5290.00 

31 

16.93 

56  .  80 

3585  .  00 

31 

13  .950 

75.00 

6250.00 

32 

15.95 

60.20 

4027.00 

32 

13.080 

81.00 

7290.00 

33 

15.08 

64.30 

'4594.00 

33 

12.310 

87.60 

8527.00 

14 

14.31 

68.60 

5230.00 

34 

11  .620 

94.20 

9860.00 

35 

13.61 

73.00 

5921  .00 

35 

11  .000 

101.00 

11330.00 

36 

13.00 

78.50 

6847.00 

36 

10.450 

108.50 

12960.00 

37 

12.45 

84.00 

7392.00 

37 

9.965 

115.00 

13580.00 

38 

11.96 

89.10 

8821  .00 

38 

9.531 

122.50 

16670.00 

39 

11.53 

95.00 

8805.00 

39 

9.145 

130.00 

18780.00 

40 

11.15 

102.50 

11650.00 

40 

202 


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Chalcopyrite         Molybdenite  Silicon 

Zincite  Pyrite 
FOR  DETECTORS  — 


$9O.OO    Per   Month 


F 


or 


Will  you  work  for  $90.00  per  month?  I  train  and  supply  the  working  force  for  most 
of  the  railroad  mileage  of  the  West,  in  telegraphy,  shorthand  and  station  work.  I  give  you  a 
thorough  and  practical  training  and  then  I  place  you  in  a  good  paying  position—  mind  you,  I 
do  not  "promise  to  assist  you,"  but  positively  guarantee  you  employment  when  competent. 
1  have  placed  1  50  during  the  past  year.  If  you  doubt  this  come  to  my  office  and  I  will  prove 
it  to  you. 

We  are  urgently  in  need  of  telegraph  operators,  assistant  agents  and  stenographers  and 
can  promise  employment  to  an  unlimited  number  of  students.  We  are  conducting  a 

MAIL    COURSE    IN    SHORTHAND 

for  the  benefit  of  those  who  cannot  conveniently  attend  the  school.  Hundreds  of  students 
taking  the  mail  course  have  been  able  to  accept  service  as  competent  stenographers  after  two 
or  three  months'  study.  We  use  Stidger's  famous  modern  shorthand,  using  but  twenty  word 
signs  as  compared  with  from  1500  to  6000  word  signs  in  the  various  Pitmanic  systems  of 
shorthand.  Ambitious  young  men  and  women  should  take  advantage  of  this  mail  course  and 
prepare  for  better  positions  during  their  spare  hours  at  home.  Complete  cost  of  mail  course 
is  $20.00.  Appiy  p.  D.  MACKAY,  Manager, 

S.  P.  Telegraph  &  Shorthand 

540-542  CENTRAL  C^U,     «.!  LOS  ANGELES 

AVE.  OCnOOI  CAL. 

Main  1570  A  1570 


W  B.  PALMER 

416  E.  Third  St. 

ELECTRICAL 
REPAIRS 

A       SPECIALTY 
i AGENT  FOR: 


Cutler-Hammer  Motor  Starting  Devices 
Crocker- Wheeler  Motors  and  Dynamos 

Have  Constantly  On  Hand 

Mica        Empire  Cloth        Linen  Tapes        Insulating  Varnishes 

Magnet  Wire  Carbon  Brushes 

Transformer  Iron  Cut  to  Order 


Woodill  &  Hulsc  Electric  Co. 

Main  Store:     2T6  S.  Main  St.,  Ill  W.  Third  St. 
Factory:     526  S.  Los  Angeles  St. 


LOS  ANGELES, CAL. 


Manufacturers  and  Dealers  in 


High  Frequency  Apparatus 
Spark  Coils,  Transformers 
Wireless  Telegraph  Supplies 

'  and  = 

EVERYTHING     ELECTRICAL 


PUBLISHERS  OF 

TEXT  BOOKS  and  TECHNICAL  WORKS 

DEALERS  IN 

Mechanical  Drawing  Instruments 
and  Supplies 

Special  Prices  to  Students 

113-115  S.  Broadway         Los  Angeles,  Cal. 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 
BERKELEY 

Return  to  desk  from  which  borrowed. 
This  book  is  DUE  on  the  last  date  stamped  below. 


, 

JAN  26  1950  / 

C^ 

I 

M 

^'Df?    4  1950  / 

/ 

MAY  1  7  195f 

SENT  ON  ILL 

' 

MAY  0  9  m 

U,C.  BERKELEY 

-. 

• 

\P3pm 

- 

PI 

> 

LD  21-100m-9,'48(B399sl6)476 


YC  33R49 


